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AU2002329643A1 - Crystallized structure of type IV collagen NC1 domain hexamer - Google Patents

Crystallized structure of type IV collagen NC1 domain hexamer

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AU2002329643A1
AU2002329643A1 AU2002329643A AU2002329643A AU2002329643A1 AU 2002329643 A1 AU2002329643 A1 AU 2002329643A1 AU 2002329643 A AU2002329643 A AU 2002329643A AU 2002329643 A AU2002329643 A AU 2002329643A AU 2002329643 A1 AU2002329643 A1 AU 2002329643A1
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sequence
amino acids
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polypeptide
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Billy Hudson
Muirathinam Sundaramoorthy
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University of Kansas Medical Center
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University of Kansas Medical Center
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Description

Crystallized structure of Type IV Collagen NCI Domain Hexamer
CROSS REFERENCE This application claims priority to U.S. Provisional Patent Application Serial
Nos. 60/308,523 filed My 27, 2001; 60/351,289 filed October 29, 2001; 60/366,854 filed March 22, 2002; and 60/385,362 filed June 3, 2002.
STATEMENT OFGOVERNMENT INTEREST This work was supported by Grants DK18381 and DK53763 from the
National Institutes of Health, and thus the U.S. government may have certain rights in the invention.
FIELD OF THE INVENTION The present invention relates to the fields of crystallography, molecular biology, protein chemistry, angiogenesis, tumor growth and metastasis, and basement membrane assembly
BACKGROUND OF THE INVENTION The basement membrane (basal lamina) is a sheet-like extracellular matrix
(ECM), which is a basic component of all tissues. The basal lamina provides for the compartmentalization of tissues, and acts as a filter for substances traveling between tissue compartments. Typically the basal lamina is found closely associated with an epithelium or endothelium in all tissues of an animal, including blood vessels and capillaries. The basal lamina components are secreted by cells and then self assemble to form an intricate extra-cellular network. The formation of biologically active basal lamina is important to the development and differentiation of the associated cells.
Type IN collagen has been shown to be a major structural component of basement membranes, and consists of a family of six homologous chains, designated l(IV) tlirough α6(IN). Each a chain is characterized by a non- collagenous (NCI) domain at the carboxyl terminus; a long, helical collagenous domain in the middle region; and a 7S collagenous domain at the amino terminus. (Martin, et. al., 1988, Adv. Protein Chem. 39:1-50; Gunwar, et. al. 1991, J. Biol. Chem. 266:14088-14094). Three chains assemble into triple helical molecules, the "heterotrimer." The heterotrimer, once formed in the endoplasmic lumen, is secreted into the extracellular space, where two such heterotrimers assemble into a hexamer via C-terminal interactions, and then into a supramolecular network through N- terminal associations. The NCI domains play the dominant role in this assembly, by determining the C-terminal dimeric association, leading to hexamer assembly. The chain composition, and thus the properties of type IN collagen networks, are influenced by two factors. First, the chain composition of networks is limited by chain availability: the six chains show a tissue-specific expression pattern, with the αl and o2 chains being ubiquitous, and the cβ-c-6 chains having a more restricted tissue distribution. Second, the ΝC1 domain confers specificity to the chain-specific assembly of networks. Thus, as yet unidentified recognition sequences must exist within the ΝC1 domain that direct the selection of chains to form triple helical protomers, and that direct triple helical protomers to form hexamers and, thus, collagen networks. While numerous type IN collagen hexamers are theoretically possible that differ in kind and chain stochiometry, only three have been identified: [cd2α2]2, [o3c-4o5]2, and [(c.l2o2)(α52α6)].
Angiogenesis, the process of formation of new blood vessels, plays an important role in physiological processes such as embryonic and postnatal development, as well as in wound repair. Formation of blood vessels can also be induced by pathological processes involving inflammation (e.g., diabetic retinopathy and arthritis) or neoplasia (e.g., cancer) (Folkman, 1985, Perspect, Biol. Med., 29, 10). Νeovascularization is regulated by angiogenic growth factors secreted by tumor or normal cells as well as by the composition of the extracellular matrix and the activity of endothelial enzymes (Nicosia and Ottinetti, 1990, Lab. Invest., 63, 115).
A common feature of all solid tumor growth is the requirement for a blood supply. Therefore, numerous laboratories have focused on developing anti- angiogenic compounds based on growth factors and their receptors. While this approach has led to some success, the number of growth factors known to play a role an angiogenesis is large. Therefore, the possibility exists that growth factor antagonists may have only limited use in treating cancer, since tumors and associated inflammatory cells likely produce a wide variety of factors that can induce angiogenesis.
In this regard, a strategy that targets a common feature of angiogenesis, such as endothelial cell adhesion to the extracellular matrix (ECM), might be expected to have a profound physiological impact on tumor growth in humans. This notion is supported by the fact that antagonists of specific ECM cell adhesion receptors such as αvB3 and αvB5 integrins can block angiogenesis. Furthermore, the αvB3 integrin is expressed most prominently on cytokine-activated endothelial and smooth muscle cells, and has been shown to be required for angiogenesis. (Narner et al., Cell Adhesion and Communication 3:367-374 (1995); Brooks et al., Science 264:569-571 (1994)). Based on these findings, a potentially powerful new approach to anti- angiogenic therapy is to specifically target critical regulatory domains within distinct ECM components.
Specific type IN collagen α(JN) ΝC1 domains have been demonstrated to be effective inhibitors of angiogenesis, tumor growth, tumor metastasis, cell binding to basement membranes, and assembly of Type IN collagen molecules (see, for example, U.S. Patent Νos. 5,691,182; 5,856,184; 6,361,994; and 6,358,735). Despite the above, it would be of significant value to the art to identify further compounds capable of inhibiting these processes. It is therefore highly desirable to provide a method of deducing the crystal structure of type IN collagen ΝC1 domains, and of providing a method of using this structure to design compounds that inhibit assembly of the type IN collagen heterotrimer and/or the type IN collagen hexamer.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a crystallized NCI domain hexamer of Type IN collagen, and methods for making the crystal, wherein the ΝC1 domain hexamer is crystallized such that the three dimensional structure of the crystallized ΝC1 domain hexamer can be determmed to a resolution of at least 3 A or better.
In another aspect, the present invention provides a method for designing compounds to inhibit angiogenesis, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and/or basal lamina assembly, comprising analyzing the three dimensional structure of a crystallized Type IV collagen NCI domain hexamer produced by the methods of the invention, and identifying and synthesizing compounds that target regions of the NCI domain that have been identified by the analysis as being important for type IN collagen heterotrimer and hexamer assembly. Such compounds can be used to inhibit angiogenesis, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly.
In another aspect, the present invention provides novel polypeptides designed by the rational drug design methods of the present invention, based on an analysis of the type IN collagen ΝC1 hexamer structure disclosed herein. As a result of the information available from the crystal structure, it is possible to predict individual ΝC1 domain sequences that are critical for assembly of the type IV collagen heterotrimer and/or hexamer. Thus, it is also possible to design therapeutic polypeptides that will interfere with those interactions, and to inhibit assembly of the type rV collagen heterotrimer and/or the type IV collagen hexamer. Such therapeutic polypeptides can be used to inhibit or disrupt type IV collagen assembly, and thus are useful to inhibit angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly.
Brief Description of the Figures Figure 1. Alignment of six human αΝCl chains grouped as αl-like (1, 3, & 5) and α2-like (2, 4, & 6) families. The cysteine pairs intrachain disulfides are labeled with identical numbers at the bottom. Six segments that form the trimer-trimer interface are boxed and three major segments at the monomer-monomer are highlighted with larger font size. The most important segments forming generic and specific interactions are identified at the bottom with darkly shaded bars, respectively.
Figure 2.(a) αl chains and (b) α2 chains. Secondary structural elements are assigned based on the crystal structure. Both αl and α2 structures contain β-strands βl-βlO and βl'-βlO' and a 310 helices gl and gl'. The differences in secondary structures are a 310 helix in αl and β-stand βp' in α2 at the equivalent regions in the two sequences. The partner of βp' strand of α2 chain is in one of the two αl chains. The corresponding region in α2 and the other αl chains are extended structures. These regions marked by boxes. The secondary structures were from PROCHECK(61). Figure 3. Stereo diagram of deduced NCI hexamer structure. The trimer-trimer interface ("Equatorial Plane"), collagen triple helical junction, and pseudo 3-fold axis or triple helix axis ("Polar Axis") are identified. The two trimers are related by a 2- fold NCS axis perpendicular to the polar axis and plane of the paper. This figure and Figs. 5, 8, 9 and 10b were made using SETOR (45).
Figure 4. (a) Illustration of αl monomer structure in the hexamer. Four β-sheet regions are identified as I, II, IF and II and three short 310 helices are also shown. Figure 5. Topology diagram of NCI trimer depicting interchain and intrachain 3D domain swapping interactions (generic assembly) and chain interfaces with different secondary structural elements (specific assembly). The secondary structural elements are labeled only for αl A chain. The β-sheets, I & II in the N-subdomain and F & IF in the C-subdomain are identified. Each subdomain has 10 β-strands (βl-βlO and βl'- βlO') and two short 310 (gl and g2') helices. Additionally there are distinct secondary structures at the three interfaces — a parallel β-sheet (βp-βp') at αlB-α2 interface and a 310 helix (gl ') and extended structure at αlA-αlB and α2-αlA interfaces.
Figure 6. a) Generic interactions in the trimer. Six-strand β-sheets formed by interchain and intrachain 3D domain swapping interactions form the major force in the trimer organization. The sheets belonging to subdomains are shown in boxes to highlight such interactions. Central β barrel-like core, shown inside the circle, also plays a role in packing and stabilizing this scaffold, (b) Unique secondary structures and prominent side chain interactions at the three interfaces are shown. The αlb-α2 interface has more number of hydrogen bonds than the other interfaces. Figure 7. Trimer-trimer interface. Comparison of essential hydrogen bonding interactions in the interface at "core" (Figure 7 A), "outer" (Figure 7B) and major- minor junction (Figure 7C) for αl-αl and αl-α2 dimers (see text for details).
Detailed Description of the Preferred Embodiments
Within this application, unless otherwise stated, the techniques utilized may be found in any of several well-known references such as: Molecular Cloning: A Laboratory Manual (Sambrook, et al., 1989, Cold Spring Harbor Laboratory Press), Gene Expression Technology (Methods in Enzymology, Vol. 185, edited by D. Goeddel, 1991. Academic Press, San Diego, CA), "Guide to Protein Purification" in Methods in Enzymology (M.P. Deutshcer, ed., (1990) Academic Press, Inc.); PCR Protocols: A Guide to Methods and Applications (Innis, et al. 1990. Academic Press, San Diego, CA), Culture of Animal Cells: A Manual of Basic Technique, 2n Ed. (R.I. Freshney. 1987. Liss, Inc. New York, NY), and Gene Transfer and Expression Protocols, pp. 109-128, ed. E.J. Murray, The Humana Press Inc., Clifton, N.J.). Type IV collagens are synthesized and assembled as heterotrimers inside the cells, which are then secreted extracellularly where hexamer assembly, and subsequent basement membrane (basal lamina) assembly, occurs.
The present work has elucidated the structure of the type IV collagen [(c-l)2(α.2)] NCI hexamer. Knowledge of this structure has utility in the design of compounds that can inhibit assembly of type TV collagen heterotrimers and hexamers, and thus are beneficial in the inhibition of angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly.
Knowledge of the structure of the type IV collagen [(c l)2(α2)]2 NCI hexamer structure provided by the present invention also has utility in the design of compounds that promote heterotrimer and hexamer assembly by providing tools and reagents for increasing the understanding of type T collagen assembly, and thus also of basal lamina/basement membrane structure and function in general.
In one aspect, the present invention is directed to the three-dimensional structure of an isolated and purified type IN collagen [(αl)2(o2)]2 ΝC1 domain hexamer ("hexamer"), such that the three dimensional structure of the crystallized type IN collagen [(cd)2(C2)]2 ΝC1 hexamer can be determined to a resolution of 3.0 A or better, preferably 2.2 A or better, and most preferably 2.0 A or better, and wherein the crystals are of space group P2l5 with an approximate a=129.41 A; approximate b=143.87 A; approximate c=162.92 A; and approximate /3=91.3°at room temperature and 4 hexamers in the asymmetric unit. Alternatively, the crystal has an approximate a=127.16 A; approximate b=139.57 A; approximate c=160.20 A; and approximate /3=91.3° and 4 hexamers in the asymmetric unit, h a further alternative, the crystals may have an approximate a=79.79A; approximate b= 137.20 A; approximate c= 126.69 A; and approximate 0=90.3° at room temperature and 2 hexamers in the asymmetric unit.
In another aspect, the invention provides a method for crystallizing a type IN collagen [(c-l) (o2)]2 ΝC1 hexamer to a resolution of less than about 3.0 A or better, preferably 2.2 A or better, and most preferably 2.0 A or better, wherein the type IN collagen [(c-l)2(o2)]2 NCI hexamer is present at a concentration of about 0.5 mg/ml to about 50 mg/ml, more preferably from about 1 mg/ml to about 15 mg/ml and most preferably about 10 mg/ml, and the crystallization takes place at 4°C to 32° C, more preferably from 10°C to 26°C, even more preferably at about 16° to 24°C, and even more preferably 20° C, to thereby obtain crystals of space group P21. The crystals may have an approximate a=129.41 A; approximate b=143.87 A; approximate c=162.92 A; and approximate (3=91.3° at room temperature and 4 hexamers in the asymmetric unit. Alternatively, cryocooling of the crystals may yield a crystal with an approximate a=127.16 A; approximate b=139.57 A; approximate c=160.20 A; and approximate β=91.3° and 4 hexamers in the asymmetric unit. In a further alternative, the crystals may have an approximate a=79.79A; approximate b= 137.20 A; approximate c= 126.69 A; and approximate (8=90.3° at room temperature and 2 hexamers in the asymmetric unit.
The crystallization, in one embodiment, may occur using hanging drops and the vapor diffusion method over 10% (w/v) PEG 20K. Alternatively, other crystallization methods may be used. For instance, a temperature variation may be used to produce crystals, or crystallization in space may be used to improve resolution. The crystallization, in another embodiment, may occur over 20% PEG 3350. In addition, other chemicals can be used in the place of PEG 20K or 3350. For instance, organic chemicals (e.g. isopropanol), inorganic chemicals (e.g. (NH4)2SO4, NaH2 PO4), and other molecular weight PEG may be used. Further details of the method are as described below.
In a further aspect, the present invention provides a method for determining the three dimensional structure of the crystallized type IN collagen [(c-l)2(o2)]2 ΝC1 hexamer, comprising the steps of crystallizing the type IN collagen [(c )2(c-2)]2 ΝC1 hexamer as described above, and then analyzing the type IN collagen [(αl)2(o2)] ΝC1 hexamer to determine its three dimensional structure. In a preferred embodiment, the analyzing is by x-ray diffraction. Data sets generated from the diffraction analysis can be analyzed using any appropriate software, including but not limited to the DEΝZO and SCALEPACK programs of the HKL2000 suite (39), the SOLVE program (40), the RESOLVE (41) program, and/or the FFT program of CCP4 suite (42). Tracing of the polypeptides from the resulting analysis can be accomplished using any suitable software, including but not limited to the TOM
FRODO graphics program (43). The final structure analysis can be accomplished using any appropriate software, including but not limited to SETOR(45), GRASP(46), and SURFNET(47) graphics software packages, various utility programs in the CCP4 suite, and HBPLUS(48) and protein-protein interaction web server (http ://www.biochem.ucl. ac .uk/bsm/ PP/server/) . By analyzing the three-dimensional structure of the type IV collagen
[(cd) (G2)]2 hexamer, one of skill in the art can determine the critical sites for type IV collagen NCI domain heterotrimer and hexamer assembly, as described below.
Another aspect of the invention is to use the three-dimensional structure of the type IN collagen [(c-l)2(o2)]2 hexamer to solve the three-dimensional structure of a different type IN collagen ΝC1 domain hexamer crystal, or crystal of a mutant, homologue or co-complex of type IN collagen ΝC1 domain hexamer.
A further aspect of this invention is to use the three-dimensional structure of type IN collagen [(c )2(α2)]2 hexamer to design inhibitors of the assembly of heterotrimers and hexamers of type IN collagen, including the type IV collagen [(o.l)2(α2)]2 ΝC1 hexamer. These inhibitors may be used as therapeutics to inhibit undesired angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly. This embodiment comprises:
(a) obtaining crystals of an ΝC1 hexamer of type TV collagen, wherein the crystal comprises an [(αl)2.α2]2 ΝC1 hexamer of type IV collagen, wherein the crystal consists of space groups P2\ with approximate a = between 127.16 A and 129.41 A, b = between 139.57A and 143.87 A; c = between 160.20 A and 162.92 A; β = 91.3°, such that the three-dimensional structure of the crystallized ΝC1 domain hexamer can be determined to a resolution of 3 A or better; (b) analyzing the three-dimensional structure of the crystallized ΝC1 domain hexamer of type IV collagen; and
(c) designing a potential inhibitor of type IV collagen assembly that targets one or more regions of a type IV collagen ΝC1 . chain selected from the group consisting of: (i) Inter-chain domain swapping region;
(ii) Intra-chain domain swapping region; (iii) Specificity region; (iv) Specificity region partner; (v) Hexamer interface; (vi) Monomer-monomer interface; and (vii) Hypervariable region. As used herein "target" or" targeting" refers to compounds that will interact with this region, via covalent or non-covalent means. The definitions of the various regions are discussed below.
As discussed above, the NCI domains drive the selection process for type IV collagen chain assembly, and thus analysis of NCI domain assembly correlates with type IN collagen assembly. Furthermore, given the high, degree of homology of the different ΝC1 domains, analysis of the [(c )2(c-2)]2 ΝC1 hexamer crystal structure provides insights into the structure of other hexamer types, as well as inhibiters of such assembly.
As used herein, "inhibiting assembly of heterotrimers and hexamers of type IN collagen" means to inhibit initial assembly of such heterotrimers and/or hexamers, or to disrupt the assembly of already assembled heterotrimers and hexamers of type IN collagen ΝC1 domains. In a highly preferred embodiment, the therapeutic compounds identified herein inhibit the initial assembly of such heterotrimers and/or hexamers of type IN collagen ΝC1 domains.
The inhibitors can comprise peptides, or antibodies directed against peptides derived from the critical regions that would be expected to interfere with type IN collagen heterotrimer and/or hexamer assembly. Alternatively, small molecules that are identified based on their potential to inhibit such assembly. Electronic screening of large, structurally diverse compound libraries, such as the Available Chemical Directory (ACD) can identify new structural classes of such modulators that would be expected to interact with the identified critical regions. Additionally, knowledge of the type IN collagen [(c l)2(c-2)]2 ΝC1 hexamer structure permits "de novo design" of compounds to inhibit assembly of any type IN collagen ΝC1 domain heterotrimers and/or hexamers.
Potential inhibitors can be examined in silico through the use of computer modeling, using a docking program such as GRAM, DOCK, or AUTODOCK [Dunbrack et al., 1997, supra]. These procedures can include computer fitting of candidate compounds to the type IN collagen [(αl)2(c-2)]2 ΝC1 hexamer to predict how the shape and chemical structure of the candidate compound will interfere with assembly of the type IN collagen heterotrimer and/or hexamer. Computer programs can also be used to estimate the attraction, repulsion, and steric hindrance of the candidate compound to the relevant binding site on the type IN collagen [(αl)2(c-2)]2 hexamer. Generally the tighter the fit (e.g., the lower the steric hindrance, and/or the greater the attractive force), the more potent the candidate compound will be, and the less likely that the candidate compound will induce significant side effects due to unwanted interactions with other proteins.
Potential small molecule inhibitors can be obtained, for example, by screening random peptide libraries produced, for example, in recombinant bacteriophage (Scott and Smith, Science, 249:386-390 (1990); Cwirla et al, Proc. Νatl. Acad. Sci., 87:6378-6382 (1990); Devlin et al, Science, 249:404-406 (1990)), or a combinatorial chemical library. Candidate compounds selected in this manner can be systematically modified by computer modeling programs until one or more promising candidate compounds are identified. Such analysis has been shown to be effective, for example, in the development of HIV protease inhibitors (Lam et al., Science 263:380-384 (1994); Wlodawer et al., Ann. Rev. Biochem. 62:543-585 (1993); Appelt, Perspectives in Drug Discovery and Design 1:23-48 (1993); Erickson, Perspectives in Drug Discovery and Design 1:109-128 (1993)).
Such computer modeling allows the selection of a finite number of rational chemical modifications, as opposed to the countless number of essentially random chemical modifications that could be made. Thus, the use of the three-dimensional structure disclosed herein, in conjunction with computer modeling, enables rapid screening in silico, which dramatically increases screening speed and efficiency.
Once such candidate compounds are identified, they are chemically synthesized, and their biological activity is assayed, as discussed below. For those compounds that show activity, they can be complexed with the type IV collagen [(c-l)2(c-2)]2 ΝC1 hexamer crystal for further X-ray diffraction analysis to map the interactions of the compound with the crystal structure. The three-dimensional structure of the supplemental crystal can be determined by Molecular Replacement Analysis, which involves using a known three-dimensional structure as a search model to determine the structure of a closely related molecule or protein-ligand complex in a new crystal form. The measured X-ray diffraction properties of the new crystal are compared with the search model structure to compute the position and orientation of the protein in the new crystal. Using this approach, it is possible to use the structure of the type IV collagen [(c-l) (α2)]2 ΝC1 hexamer disclosed herein to solve the three-dimensional structures of any such type IV collagen hexamer or co- complex.
Functional Assays Any assay that can be used to test the effect of the candidate compounds on the in vitro or in vivo assembly of type IV collagen heterotrimers and/or hexamers can be used to verify the efficacy of the candidate compounds identified by the methods of the invention. Furthermore, any assay that can be used to test the effect of the candidate compounds on angiogenesis, tumor growth, tumor metastasis, and endothelial cell adhesion and/or motility can be used to verify their inhibitory activity. Such assays include, but are not limited to, the following.
Assembly assay
In one example, the methods employed are as described in Boutaud et al., JBC 275 (39):30716-30724 (2000). Native GBM hexamers are isolated by standard methods and dissociated by dilution (<50 jUg/ml) into a solution of 50 mM formic acid buffered at pH 3.0 with Tris base. Under these conditions, complete dissociation to NCI monomers and dimers occurs, as can be verified by HPLC or FPLC gel filtration. The absence of salt from the buffer is optimal for complete hexamer dissociation. Reassembly of the dissociated NCI domains is performed by changing the buffer to Tris-buffered saline (50mM Tris, pH 7.4, 150mM NaCl) by repeated dilution-concentration cycles. After incubating the NCI domains at a concentration of about 1 mg/ml for 24 hours at room temperature, in the presence or absence of the candidate compounds at a desired concentration(s), the reaction products are separated according to their molecular weights using gel filtration chromatography. Quantification of the relative amounts of the various species in the mixture is done by peak area analysis from the HPLC profiles. Hexamer assembly from purified c -c-6 NCI domains is carried out similarly. h all experiments, the ratio of the NCI domains in the association mixture is preferably kept at 1:1. The isolated NCI hexamers can subsequently be analyzed for composition by immunoprecipitation followed by Western blotting; for overall appearance (size and shape) by electron microscopy; and for molecular weight by sedimentation equilibrium ultracentrifugation. In Vitro Effect on Angiogenesis
With modifications, the procedures of Nicosia and Ottinetti, (1990, Lab. Invest., 63, 115) and Nicosia, et. al. (1994, Exp. Biology, 164, 197-206) are utilized for experiments designed to test the effect of the drug candidates on angiogenesis under in vitro conditions. The model has been used to study the effects of growth factors and extracellular matrix molecules on the angiogenic response, and employs aortic ring cultures in three-dimensional collagen gels under serum-free conditions.
Experiments are performed with 1-3 month old Swiss Webster male mice. Following anesthesia, the thoracic aorta is excised under aseptic conditions and transferred to sterile MCDB 131 sterile growth medium (Clonetics, San Diego, CA) containing antibiotics. Fat is dissected away from the aorta and approximately six to eight 1 mm thoracic segments are obtained from each specimen. Segments are transferred to 48 well tissue culture plates. The wells of these plates are layered with 100 microliters of Matrigel™ (EHS basement membrane, Collaborative Biomedical Products, Bedford, MA) prior to transfer of the aortic segments. The Matrigel™ is diluted 1:1 with MCDB 131 growth medium prior to use. The segments are centered in the wells and an additional 100 microliters of Matrigel™ is then placed over the specimens. The aortic segments are therefore embedded in the basement membrane matrix. Each well then receives 300 microliters of MCDB 131 growth medium. The plates are placed in an incubator maintained at 37° C with 5% CO2. Specimens are observed daily over a 7 day period. Newly growing microvessels are counted using an inverted phase microscope at various times during the culture period. To test for the effect of drug candidates on angiogenesis, the drug candidates are mixed with the Matrigel™ and with the MCDB 131 growth medium, and the growth of microvessels from the cultured tissue into the matrix is analyzed.
Subcutaneous fibrin implant angiogenesis
The drug candidates are injected intravenously into rats containing fibrin implants surgically placed subcutaneously, a modified version of the method described by Dvorak et al. ( Lab. Invest. 57(6):673-686 (1987)). For example, rats are given tail vein injections of either control, or various concentrations of the drug candidates. The implants are then removed at appropriate times, and directly analyzed using an inverted microscope. The analysis involved counting the number of blood vessels per implant that grow into the fibrin in the control and experimental group.
Chick embryo CAM angiogenesis assay Angiogenesis is induced in the CAMs of 10 day old chick embryos with bFGF as described (Brooks et al, Cell 92:391-400 (1998)). Twenty four hours later, the embryos are systemically treated with various concentrations of the drug candidates, in a total volume of 100 μl of sterile phosphate buffered saline (PBS). Two days later, the embryos are sacrificed and the filter discs and CAM tissues removed. Angiogenesis is quantitated by counting the number of angiogenic blood vessel branch points in the confined area of the filter disc. The Angiogenic Index is defined as the number of branch points from experimental treatment minus control treatment.
Chick embryo tumor growth assay Briefly, single cell suspensions of distinct tumor types are applied to the CAM of 10 day old chick embryos. The tumors may include, for example, CS-1 Melanoma cells, HT1080 human fibrosarcoma cells, and Hep-3 human epidermoid carcinoma cells. The embryos are injected systemically with varying concentrations of the drug candidates 24 hours later. The embryos are allowed to incubate for a total of 7 days, at which time they are sacrificed. The resulting tumors are resected and wet weights determined compared to control.
Immobilized NCI domains support human endothelial cell adhesion
In order for new blood vessels to form, endothelial cells must have the capacity to adhere and migrate through the ECM. Moreover, this endothelial cell-
ECM interaction may facilitate signal transduction events required for new blood vessel formation. Therefore, the ability of drug candidates to support endothelial cell attachment can be assessed.
Microtiter plates are coated with varying amounts of the drug candidates, followed by incubation with 1% bovine serum albumin (BSA) to block non-specific interactions. Endothelial cells, such as human ECV304 cells, are then allowed to attach to the immobilized polypeptides for varying time periods Non-adherent cells are removed by washing and attached cells are quantified by measuring the optical density of crystal violet eluted from attached cells. In vitro Endothelial Cell Migration
Invasive cellular processes, such as angiogenesis and tumor metastasis, also require cellular motility. Thus, the ability of the drug candidates to support human endothelial cell migration can be tested in vitro. These experiments are conducted essentially according to the methods in Brooks et al., J. Clin. Invest. 99:1390-1398
(1997).
In vivo Endothelial Cell Migration The ability of the drug candidates to support human endothelial cell migration can be tested in vivo. For example, drug candidates can be tested in the metastatic Lewis lung mouse tumor model using a standard protocol which is considered to be a good model of both metastasis and angiogenesis of lung tumors. (See for example, Teicher et al., Anticancer Res. 18:2567-2573 (1998); Guibaud et al., Anticancer Drugs 8:276-282 (1997); Anderson et al., Cancer Res. 56:715-718 (1996)).
Drug candidates are administered intravenously once every 2 days for a desired number of doses starting one day after tumor inoculation. All animals are weighed twice a week throughout the study. Starting one day after the last treatment, 1 or more mice are periodically sacrificed from each control group to measure pulmonary tumor burden. The experiment is terminated when the lungs of control animals have sufficient tumor mass to provide meaningful evaluation. At that time, the lungs of all remaining animals are excised, weighed, and the number of tumor foci greater than 2 mm in diameter counted. hi another aspect, the present invention provides an inhibitor of type IV collagen assembly identified by any of the methods described above.
In another aspect, the present invention provides an inhibitor of one or more process selected from the group consisting of angiogenesis, tumor growth, tumor metastasis, endothelial cell adhesion, endothelial cell proliferation, and basal lamina assembly, identified by any of the methods described above. In another aspect, the present invention provides novel polypeptides that can be used to inhibit or disrupt type TV collagen assembly, and thus are useful to inlnbit angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly. The term "polypeptide" is used in its broadest sense to refer to a compound of two or more subunit amino acids, amino acid analogs, or peptidomimetics. The subunits are linked by peptide bonds. The polypeptides described herein may be chemically synthesized or recombinantiy expressed. Preferably, the polypeptides of the present invention are chemically synthesized. Synthetic polypeptides, prepared using the well known techniques of solid phase, liquid phase, or peptide condensation techniques, or any combination thereof, can include natural and unnatural amino acids. Amino acids used for peptide synthesis may be standard Boc (Nα-amino protected Nα-t-butyloxycarbonyl) amino acid resin with the standard deprotecting, neutralization, coupling and wash protocols of the original solid phase procedure of Merrifield (1963, J. Am. Chem. Soc. 85:2149- 2154), or the base-labile Nα-amino protected 9-fluorenylmethoxycarbonyl (Fmoc) amino acids first described by Carpino and Han (1972, J. Org. Chem. 37:3403-3409). Both Fmoc and Boc Nα-amino protected amino acids can be obtained from Sigma, Cambridge Research Biochemical, or other chemical companies familiar to those skilled in the art. hi addition, the polypeptides can be synthesized with other Not- protecting groups that are familiar to those skilled in this art.
Solid phase peptide synthesis may be accomplished by techniques familiar to those in the art and provided, for example, in Stewart and Young, 1984, Solid Phase Synthesis, Second Edition, Pierce Chemical Co., Rockford, 111.; Fields and Noble, 1990, h t. J. Pept. Protein Res. 35:161-214, or using automated synthesizers. The polypeptides of the invention may comprise D-amino acids (which are resistant to L- amino acid-specific proteases in vivo), a combination of D- and L-amino acids, and various "designer" amino acids (e.g., 3-methyl amino acids, Cot-methyl amino acids, and Nσ.-methyl amino acids, etc.) to convey special properties. Synthetic amino acids include ornithine for lysine, fluorophenylalanine for phenylalanine, and norleucine for leucine or isoleucine.
In addition, the polypeptides can have peptidomimetic bonds, such as ester bonds, to prepare peptides with novel properties. For example, a peptide may be generated that incorporates a reduced peptide bond, i.e., and R2 are amino acid residues or sequences. A reduced peptide bond may be introduced as a dipeptide subunit. Such a polypeptide would be resistant to protease activity, and would possess an extended half-live in vivo. As discussed above, type IV collagens are synthesized and assembled as heterotrimers inside the cells, which are then secreted extracellularly where hexamer assembly, and subsequent basement membrane assembly, occurs. The polypeptides disclosed herein can work intra-cellularly to prevent heterotrimer assembly, which also necessarily inhibits hexamer assembly, and provide the desired therapeutic result. Alternatively (or additionally), the polypeptides disclosed herein can work extracellularly, to inhibit hexamer assembly, and/or to disrupt assembled hexamers, providing the desired therapeutic result.
Such polypeptides can be selected based on their utility in inhibiting generic heterotrimer assembly (ie: not chain specific); specific heterotrimer assembly (ie: chain specific); generic hexamer assembly (ie: not chain specific); and/or specific hexamer assembly (ie: not chain specific). Without knowledge of the type IV collagen [(c-l)2(o-2)]2 NCI hexamer structure described herein, the design of inhibitors with such desired properties would not be available to those skilled in the art. The single letter abbreviation for amino acids is used herein; "norL" refers to nor leucine.
In one embodiment, the polypeptides consist of at least 8 contiguous amino acids of general formula I:
PF(R1)(R2)CN(R3)(R4)(R5)VC(R6)(R7)A (SEQ ID NO:l) RI is selected from the group consisting of L, M, A, V, norL, and I;
R2 is selected from the group consisting of F and Y;
R3 is selected from the group consisting of I, V, L, norL, A, and P;
R4 is selected from the group consisting of N, G, and H;
R5 is selected from the group consisting of N, D, Q, and E; R6 is selected from the group consisting of N, Y, and H; and
R7 is selected from the group consisting of F and Y.
This general formula I is derived from a consensus sequences of type IV collagen NCI al-a6 domains at the inter-chain domain swapping region ("Inter- CDSR") that includes the ββ-βl strands in the crystal structure, as further described below. This region is involved in interchain interactions within the heterotrimer, and a substantial portion of the sequence is also present at the hexamer interface, and thus is involved in hexamer assembly/stabilization. As such, peptides of general formula I are useful for inhibiting appropriate interchain interactions, and thus for disrupting optimal heterotrimer and hexamer assembly.
In various further embodiments, the polypeptides consists of at least 9, 10, 11, 12, 13, or 14 amino acids of general formula I. In a preferred embodiment, the polypeptide consists of 14 amino acids of general formula I.
In a preferred embodiment, the polypeptides consist at least 8 contiguous amino acids of general formula II, with the further limitation that R2 is F; R4 is N; R5 is selected from the group consisting of N and D; R6 is N; and R7 is F. Polypeptides of this embodiment are derived from a consensus sequences of type IV collagen NCI αl, oβ, and α5 domains at the Inter-CDSR.
In a further preferred embodiment, the polypeptides consist at least 8 contiguous amino acids of general formula I, with the further limitation that R2 is Y; R3 is selected from the group consisting of P and I; R5 is selected from the group consisting of D, Q, and E; R6 is selected from the group consisting of Y and H; and R7 is Y. Polypeptides of this embodiment are derived from a consensus sequences of type TV collagen NCI α2, α4, and α6 domains at the hiter-CDSR.
In a further preferred embodiment, the polypeptides according to formula 1 consist of at least 8 contiguous amino acids of a sequence selected from the group consisting of PFLFCNLNNVCNFA (αl) (SEQ ID NO:2); PFLFCNVNDVCNFA (off) (SEQ ID NO:3); PFMFCNINNVCNFA (α5) (SEQ ID NO:4); PFLYCNPGDVCYYA (α2) (SEQ ID NO:5); PFAYCNTHQVCHYA (α4) (SEQ ID NO:6); and PFIYCNINEVCHYA (α6) (SEQ ID NO:7). These sequences represent the Inter-CDSR sequences from the individual type IV collagen αl -α6 NCI domains. In various further embodiments, the polypeptides consist of at least 9, 10, 11, 12, 13, or 14 amino acids of one of the recited sequences. In a preferred embodiment, the polypeptide consists of 14 amino acids of one of the recited sequences.
In another embodiment, the polypeptides of the present invention consist of at least 7 contiguous amino acids of general formula II:
PF(R1)EC(R2)G(R3)(R4)GTC(R5) (SEQ ID NO:8) RI is selected from the group consisting of L, A, V, norL, and I;
R2 is selected from the group consisting of H, N, Q, and S;
R3 is selected from the group consisting of G, R, A, or is absent;
R4 is selected from the group consisting of R and Q; and
R5 is selected from the group consisting of N and H. This general formula is derived from a consensus sequences of type IN collagen NCI αl -α6 domains at the intra-chain domain swapping region ("fiitra- CDSR") that includes the ββ'-βl' strands in the crystal structure, as further described below. This region is involved in monomer-monomer interactions within the heterotrimer, and a substantial portion of the sequence is also present at the hexamer interface, and thus is involved in hexamer assembly/stabilization. As such, peptides of this general formula are useful for inhibiting both heterotrimer and hexamer interactions of type IN collagen.
In various further embodiments, the polypeptides consists of at least 8, 9, 10, 11, 12, or 13 amino acids of general formula II. In a preferred embodiment, the polypeptide consists of 13 amino acids of general formula II.
In a preferred embodiment, the polypeptides consist at least 7 contiguous amino acids of general formula II, with the further limitation that R2 is H; R3 is R; R4 is G; and R5 is Ν. Polypeptides of this embodiment are derived from a consensus sequence of the intra-CDSR sequences of the type IN collagen αl, α3, and α5 ΝC1 domains.
In a further preferred embodiment, the polypeptides consist at least 7 contiguous amino acids of general formula II, with the further limitation that R2 is selected from the group consisting of Ν, Q, and S; R3 is selected from the group consisting of G, R, and A; R4 is selected from the group consisting of R and Q; and R5 is H. Polypeptides of this embodiment are derived from a consensus sequence of the intra-CDSR sequences of the type IN collagen α2, α4, and α6 ΝC1 domains.
In a further embodiment, the polypeptides according to general formula II consist of at least 7 contiguous amino acids of a sequence selected from the group consisting of PFIECHGRGTCN (αl and α5) (SEQ ID NO:9); PFLECHGRGTCN (α3) (SEQ ID NO:10); PFTECNGGRGTCH (α2) (SEQ ID NO:ll); PFLECQGRQGTCH (α4) (SEQ ID NO:12); and PFLECSGARGTCH (α6) (SEQ ID NO:13). These sequences represent the h tra-CDSR sequences from the individual type IN collagen αl -α6 ΝC1 domains. In various further embodiments, the polypeptides of this embodiment consist of at least 8, 9, 10, 11, 12, or 13 amino acids of one of the recited sequences. In a most preferred embodiment, the polypeptides consist of 12 (αl, α3, α5) or 13 (α2, α4, α6) contiguous amino acids of any one the recited sequences. In a further embodiment, the full length h tra-CDSR polypeptides (e.g.: SEQ ID NO: 9, 10, 11, 12, or 13) may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Thus, the polypeptides of the invention derived from the Intra-CDSR sequence of the αl-like NCI chains can thus be selected from the group consisting of at least 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22 amino acids of a sequence selected from the group consisting of: αl: (E)(F)(R)(S)(A) PFIECHGRGTCN(Y)(Y)(A)(N)(A) (SEQ ID NO:14), α3: (E)(F)(R)(A)(S)PFLECHGRGTCN(Y)(Y)(S)(N)(S) (SEQ ID NO: 15); and o5: (E)(F)(R)(S)(A)PFlECHGRGTCN(Y)(Y)(A)(N)(S) (SEQ ID NO: 16); wherein the residues in parenthesis are the flanking sequences of the Intra-
CDSR.
Alternatively, the polypeptides of the invention derived from the Intra-CDSR sequence of the α2-like NCI chains can thus be selected from the group consisting of at least 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23 amino acids of a sequence selected from the group consisting of: α2: (D)(F)(R)(A)(T)PFIECNGGRGTCH(Y)(Y)(A)(N)(K) (SEQ ID NO: 17); α4: (D)(F)(R)(A)(A)PFLECQGRQGTCH(F)(F)(A)(N)(K) (SEQ ID NO: 18); and α6: (D)(F)(R)(A)(T)PFIECSGARGTCH(Y)(F)(A)(N)(K) (SEQ ID NO: 19); wherein the residues in parenthesis are the flanking sequences of the Intra- CDSR.
The Inter CDSR sequence, while widely separated in the linear sequence of a given type IN collagen ΝC1 domain from the Intra-CDSR sequence in the same α chain (separated by approximately 100 amino acids), is present in close spatial proximity (within approximately 2 amino acids) to the hiter-CDSR sequence in the same α chain based on the derived crystal structure data. Thus, in another embodiment, the present invention provides chimeric polypeptides comprising:
(a) one or more Inter-CDSR polypeptides of general formula I;
(b) one or more Intra-CDSR polypeptides of general formula II; and (c) a linker polypeptide between the hitra-CDSR polypeptide and the Inter-
CDSR polypeptide consisting of between 0-20 amino acids.
In preferred embodiments, the Inter-CDSR and/or the Intra-CDSR portion of the chimeric polypeptides consists of 8, 9, 10, 11, 12, 13, or 14 amino acids of general formula I and 7, 8, 9, 10, 11, 12, 13 amino acids of general formula II, respectively. In various other preferred embodiments, the linker polypeptide consists of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acids. The optimal length of the spacer depends, at least in part, on the length of the Inter-CDSR and Intra-CDSR, as well as the position of the sequences within the full length Inter- CDSR and Intra-CDSR used to create the chimera. For example, if a full length friter- CDSR and a full length Intra-CDSR were used, then the spacer is preferably between 0-5 amino acids in length, more preferably between 1-4 amino acids in length, and most preferably 2-3 amino acids in length. Based on the teachings herein, it will be apparent to one of skill in the art to design further such chimeric polypeptides.
In a most preferred embodiment of these chimeric polypeptides, the Inter- CDSR polypeptide is selected from the group consisting of PFLFCNINNNCNFA (SEQ ID NO:2), PFLFCNVNDVCNFA (SEQ ID NO:3), PFMFCNINNNCNFA (SEQ ID NO:4), PFLYCNPGDVCYYA (SEQ ID NO:5), PFAYCNIHQVCHYA (SEQ ID NO:6), and PFIYCNINEVCHYA (SEQ ID NO:7); the Intra-CDSR polypeptide is selected from the group consisting of PFIECHGRGTCN (SEQ ID NO:9), PFLECHGRGTCN (SEQ ID NO:10), PFIECNGGRGTCH (SEQ ID NO:ll), PFLECQGRQGTCH (SEQ ID NO:12), and PFIECSGARGTCH (SEQ ID NO:13); and the linker polypeptide is 1, 2, 3, 4, or 5 amino acids; most preferably 2 amino acids.
In another embodiment, the polypeptides of the present invention consist of a sequence of an amino acids of general formula III: F(R1)T(R2) (SEQ ID NO:20) wherein RI is selected from the group consisting of S and T; and R2 is selected from the group consisting of M and L. This general formula III is derived from a consensus sequences of type TV collagen NCI αl-α6 domains at the specificity region ("SR") between the β5-ββ strands in the crystal structure, as further described below. This region is involved in specific recognition between monomers, by recognizing the specificity region partner ("SRP") in the monomer with which the SR of a given α chain interacts As such, peptides of general formula III are useful for inhibiting both heterotrimer and hexamer interactions of type IV collagen.
In a further embodiment, the SR polypeptides are selected from the group consisting of FSTM (αl, α2, α5, and α6) (SEQ ID NO:21), FTTM (α3) (SEQ ID NO:22) and FTSL (α4) (SEQ ID NO:23).
In a further embodiment, the SR polypeptides (e.g.: SEQ ID NO:21, 22, and 23) may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Thus, according to this embodiment, the polypeptides of the invention derived from the SR sequence of the NCI chains can be selected from the group consisting of: αl X1-FSTM-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLRK (SEQ ID NO: 24), and Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLFC (SEQ ID NO: 25) (the full sequence would thus be SCLRKFSTMPFLFC) (SEQ ID NO: 26); α3: X3-FTTM-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLQR (SEQ ID NO: 27), and Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLFC(SEQ ID NO: 25) (the full sequence would thus be SCLQRFTTMPFLFC) (SEQ ID NO :28); α5: X5-FSTM-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLRR (SEQ ID NO: 29), and Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFMFC (SEQ ID NO: 30) (the full sequence would thus be SCLRRFSTMPFMFC) (SEQ ID NO: 31); α2: X2-FSTM-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLAR (SEQ ID NO: 32), and Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLYC (SEQ ID NO: 33) (the full sequence would thus be SCLARFSTMPFLYC) (SEQ ID NO: 34); α4: X4-FSTL-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLPV (SEQ ID NO: 35), and Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFAYC (SEQ ID NO: 36) (the full sequence would thus be SCLPVFSTLPFAYC) (SEQ ID NO: 37); and α6: X6-FSTM-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLPR (SEQ ID NO: 38), and Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFIYC (SEQ ID NO: 39) (the full sequence would thus be SCLPRFSTMPFIYC) (SEQ ID NO: 40).
hi another embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula IV:
(R1)MF(R2)K (SEQ ID NO:41) wherein RI is selected from the group consisting of E, R, and D; and R2 is selected from the group consisting of K, R, and S. This general formula TV is derived from a consensus sequences of type IV collagen NCI αl, α3, and α5 domains at the specificity region partner ("SRP") located between the /38' and |89' strands, as discussed in more detail below. This region is involved in specific recognition between monomers, by recognizing the specificity region ("SR") in the monomer with which the SRP of a given chain interacts As such, peptides of general formula IN are useful for inhibiting both heterotrimer and hexamer interactions of type IV collagen.
In a preferred embodiment, the SRP polypeptides according to general formula TV are selected from the group consisting of EMFKK (αl) (SEQ ID ΝO:42), RMFRK (α3) (SEQ ID NO:43), and DMFSK (α5) (SEQ ID NO:44). In a further preferred embodiment, the SRP polypeptides are selected from the group consisting of SFQ (SRP of α2) (SEQ ID NO:45); LQF (SRP of α4) (SEQ ID NO:46), and QQF (SRP of α6) (SEQ ID NO:47). These sequences represent the SRP of the type IV collagen α chain NCI domains as indicated. This region in the α2 NCI domain adopts an extended conformation and pairs with the extended structure (Phe57-Thr59) in the adjacent αl chain to form a short parallel β sheet, which is the only parallel (8-sheet in the entire structure, as further discussed below.
In a further embodiment, the SRP polypeptides (e.g.: SEQ ID NOS:42-47) may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. The SRP-containing polypeptides of this embodiment of the invention can thus be selected from the group consisting of: αl X1-EMFKK-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TIERS (SEQ ID NO: 48), and wherem Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PTPST (SEQ ID NO: 49) (the full length sequence would thus be TIERSEMFKKPTPST) (SEQ ID NO: 50); α3: X3-RMFRK-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLNPE (SEQ ID NO: 51), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PIPST (SEQ ID NO: 52) (the full length sequence would thus be SLNPERMFRKPIPST) (SEQ ID NO:53); α5: X5-DMFSK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVDVS (SEQ ID NO: 54), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PQSET (SEQ ID NO: 55) (the full length sequence would thus be TVDVSDMFSKPQSET (SEQ ID NO: 56); α2: X2-SFQ-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TTPEQ (SEQ ID NO: 57), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSPSA (SEQ ID NO: 58) (the full length sequence would thus be TIPEQSFQGSPSA) (SEQ ID NO: 59); α4: X4-LQF-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVKAD (SEQ ID NO: 60), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SSAPA (SEQ ID NO: 61) (the full length sequence would thus be TVKADLQFSSAPA) (SEQ ID NO: 62); and cώ: X6-QQF-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVEER (SEQ ID NO: 63), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GELPV (SEQ ID NO: 64) (the full length sequence would thus be TVEERQQFGELPV) (SEQ ID NO: 65).
In another embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula V:
(R1)AH(R2)QD (SEQ ID NO:66) wherein RI is selected from the group consisting of R and K; and
R2 is selected from the group consisting of G and N. This general formula V is derived from a consensus sequences of type IV collagen NCI domain j8-barrel-like core at the β4 strand, as discussed in more detail below. This region is involved in generic monomer-monomer interactions. As such, peptides of general formula V are useful for inhibiting both heterotrimer and hexamer interactions of type IV collagen.
In a preferred embodiment, the polypeptides according to general formulaV are selected from the group consisting of RAHGQD (αl, α3, α5) (SEQ ID NO:67) and KAHNQD (α2,α4, α6) (SEQ ID NO:68).
In a further preferred embodiment, the (8-barrel polypeptides according to general formula V (e.g.: SEQ ID NOS:67-68) may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. The jS-barrel-containing polypeptides of this embodiment of the invention can thus be selected from the group consisting of: αl X1-RAHGQD-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNE (SEQ ID NO: 69), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTAG (SEQ ID NO: 70) (the full length sequence would thus be VQGNERAHGQDDLGTA) (SEQ ID NO: 71); α3: X3-RAHGQD-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNQ (SEQ ID NO: 72), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTLG (SEQ ID NO: 73) (the full length sequence would thus be VQGNQRAHGQDLGTLG) (SEQ ID NO:74); α5: X5-RAHGQD-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNK (SEQ ID NO: 75), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTAG (SEQ ID NO: 70) (the full length sequence would thus be VQGNKRAHGQDLGTAG (SEQ ID NO: 76); α2: X2-KAHNQD-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FEGQE (SEQ ID NO: 77), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGLAG (SEQ ID NO: 78) (the full length sequence would thus be FEGQEKAHNQDLGLAG) (SEQ ID NO: 79); α4: X4-KAHNQD-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LEGQE (SEQ ID NO: 80), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGLAG (SEQ ID NO: 78) (the full length sequence would thus be LEGQEKAHNQDLGLAG) (SEQ ID NO: 81); and α6: X6-KAHNQD-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VEGQE (SEQ ID NO: 82), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGFAG (SEQ ID NO: 83) (the full length sequence would thus be VEGQEKAHNQDLGFAG) (SEQ ID NO: 84).
In another embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula VI: (R1)G(R2)GQ (SEQ ID NO:85) wherein RI is selected from the group consisting of E and Q; and
R2 is selected from the group consisting of S, T, and G.
This general formula VI is derived from a consensus sequences of type IN collagen ΝC1 domain (8-barrel-like core at the (84' strand, as discussed in more detail below. This region is involved in generic monomer-monomer interactions. As such, peptides of general formula NI are useful for inhibiting both heterotrimer and hexamer interactions of type IN collagen.
In a preferred embodiment, the polypeptides according to general formula NI are selected from the group consisting of EGSGQ (αl, α5) (SEQ ID ΝO:86), EGTGQ (α3) (SEQ ID NO:87), EGGGQ (α2, α6) (SEQ ID NO:88) and QGGGQ (α4) (SEQ ID NO:89).
In a further embodiment, the j8-barrel polypeptides according to general formula VI (e.g.: SEQ ID NOS:86-89) may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. The (8-barrel-containing polypeptides of this embodiment of the invention can thus be selected from the group consisting of: αl and α5 X1-EGSGQ-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TSAGA (SEQ ID NO: 90), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALASP (SEQ ID NO: 91) (the full length sequence would thus be TSAGAEGSGQALASP) (SEQ ID NO: 92); α3: X3-EGTGQ-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TSAGS (SEQ ID NO: 93), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALASP (SEQ ID NO: 91) (the full length sequence would thus be TSAGSEGTGQALASP) (SEQ ID NO:94); α2: X2-EGGGQ-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAAGD (SEQ ID NO: 95), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLNSP (SEQ ID NO: 96) (the full length sequence would thus be TAAGDEGGGQSLVSP) (SEQ ID NO: 97); α4: X4-QGGGQ-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TGAGD (SEQ ID NO: 98), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALMSP (SEQ ID NO: 99) (the full length sequence would thus be TGAGDQGGGQALMSP) (SEQ ID NO: 100); and cώ: X6-EGGGQ-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAAGA (SEQ ID NO: 101), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLVSP (SEQ ID NO: 96) (the full length sequence would thus be TAAGAEGGGQSLVSP) (SEQ ID NO: 102).
In another embodiment, the polypeptides comprise sequences present at the hexamer interface, as determined from the deduced crystal structure. Type TV collagens are synthesized and assembled as trimers inside the cells, which are then secreted extracellularly where hexamer assembly, and subsequent basement membrane assembly, occurs. Therapeutics, such as those disclosed herein, can work intra-cellularly to prevent trimer assembly, thus inhibiting hexamer assembly, thus providing the desired therapeutic result. Alternatively (or additionally), therapeutics can work extracellularly, which leaves trimer assembly uninhibited, but targets hexamer assembly. As such, polypeptides from regions at the hexamer interface can be used to inhibit hexamer formation or disrupt hexamer formation. In this embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula VII:
(R1)G(R2)(R3) (SEQ ID NO:103) wherein RI is selected from the group consisting of Q and E;
R2 is selected from the group consisting of N and Q; and
R3 is selected from the group consisting of E, Q, and K.
Tins general formula VII is derived from a consensus sequences of type TV collagen NCI αl-α6 domains at the hexamer interface at the end of the β3 strand up to the beginning of the /34 strand, as discussed in more detail below. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula VII are useful for inhibiting hexamer interactions of type IV collagen. In a preferred embodiment, the polypeptides consist of general formula VII, with the further limitation that RI is Q and R2 is N. In this embodiment, the formula is a consensus of the sequences present in the αl/α3/α5 NCI domains for general formula VII. In a further preferred embodiment, the polypeptides according to general formula VII are selected from the group consisting of QGNE (αl) (SEQ ID NO:104), QGNQ (α3) (SEQ ID NO:105), and QGNK(α5) (SEQ ID NO:106)
In a further preferred embodiment, the polypeptides according to general formula VII consist of EGQE (SEQ ID NO:107), which is the sequence of the sequences present in the α2/α4/α6 NCI domains in general formula VII.
In a further embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS: 104-107 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: X1-QGNE-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYV (SEQ ID NO: 108), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO: 109) (the full length sequence would thus be SLLYVQGNERAHGQ) (SEQ ID NO: 110); α3: X3-QGNQ-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SFLFV (SEQ ID NO: 111), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO: 109) (the full length sequence would thus be SFLFVQGNQRAHGQ) (SEQ ID NO:112); α5: X5-QGNK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYV (SEQ ID NO:108), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO: 109) (the full length sequence would thus be SLLYVQGNKRAHGQ) (SEQ ID NO: 113);
02: X2-EGQE-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYF (SEQ ID NO:114), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO:115) (the full length sequence would thus be SLLYFEGQEKAHNQ) (SEQ ID NO: 116); α4: X4-EGQE-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYL (SEQ ID NO: 117), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO:l 15) (the full length sequence would thus be SLLYLEGQEKAHNQ) (SEQ ID NO: 118); and α6: X6-EGQE-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLFV (SEQ ID NO:119), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO: 115) (the full length sequence would thus be SLLFVEGQEKAHNQ) (SEQ ID NO: 120).
An especially preferred embodiment of these hexamer interface polypeptides according to general formula VII consists of 1 additional amino acid at both the amino and carboxy terminus of the αl-α6 hexamer peptides, as follows: αl VQGNER (SEQ ID NO: 121) α3 VQGNQR (SEQ ID NO: 122) α5 VQGNKR (SEQ ID NO: 123) o2 FEGQEK (SEQ ID NO: 124) α4 LEGQEK (SEQ ID NO: 125) α6 VEGQEK (SEQ ID NO: 126)
In a further embodiment wherein the polypeptides comprise sequences present at the hexamer interface, as determined from the deduced crystal structure, the polypeptides of the invention consist of an amino acid sequence of general formula VIII:
M(R1)M(R2)P (SEQ ID NO:127) wherein RI is selected from the group consisting of S, N, or is absent; and
R2 is selected from the group consisting of A, Q, or is absent.
This general formula VIII is derived from a consensus sequences of type IV collagen NCI l-cώ domains at the hexamer interface between the j88 and β9 strands, as discussed in more detail below. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula VIII are useful for inhibiting hexamer interactions of type IV collagen. In a preferred embodiment, the polypeptides of general formula VIII are selected from the group consisting of MSMAP (αl) (SEQ ID NO:128), MNMAP (cθ) (SEQ ID NO:129), MSMQP (α5) (SEQ ID NO:130), and MMP (c-2, α4, and α6) (SEQ ID NO: 131). h a further preferred embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS:128-131 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: Xl-MSMAP-Zl, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PEPMP (SEQ ID NO: 132), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ITGEN (SEQ ID NO: 133) (the full length sequence would thus be PEPMPMSMAPITGEN) (SEQ ID NO: 134); α3: X3-MNMAP-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PALMP (SEQ ID NO: 135), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ITGRA (SEQ ID NO: 136) (the full length sequence would thus be PALMPMNMAPITGRA) (SEQ ID NO:137); α5: X5-MSMQP-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PEPMP (SEQ ID NO:132), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LKGQS (SEQ ID NO: 138) (the full length sequence would thus be PEPMPMSMQPLKGQS) (SEQ ID NO: 139);
02: X2-MMP-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAPLP (SEQ ID NO:140), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VAEDE (SEQ ID NO:141) (the full length sequence would thus be TAPLPMMPVAEDE) (SEQ ID NO: 142); α4: X4-MMP-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AAPLP (SEQ ID NO:143), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LSEEA (SEQ ID NO:144) (the full length sequence would thus be AAPLPMMPLSEEA) (SEQ ID NO: 145); and α6: X6-MMP-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAPTP (SEQ ID NO:146), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VSQTQ (SEQ ID NO:147) (the full length sequence would thus be
TAPIPMMPVSQTQ) (SEQ ID NO: 148). An especially preferred embodiment of these hexamer interface peptides according to general formula VIII consists of 3 additional amino acids at both the amino and carboxy terminus of the αl-α6 hexamer peptides, as follows: αl PMPMSMAPITG (SEQ ID NO: 149); α3 LMPMNMAPITG (SEQ ID NO:150); α5 PMPMSMQPLKG (SEQ ID NO: 151); α2 PLPMMPVAE (SEQ ID NO: 152); α4 PLPMMPLSE (SEQ ID NO: 153); and otβ PIPMMPVSQ (SEQ ID NO: 154).
In a further embodiment wherein the polypeptides comprise sequences present at the hexamer interface, as determined from the deduced crystal structure, the polypeptides of the invention consist of an amino acid sequence of general formula IX:
AG(R1)(R2) (SEQ ID NO:155) wherein RI is selected from the group consisting of A, S and D; and
R2 is selected from the group consisting of E and Q.
This general formula IX is derived from a consensus sequences of type IV collagen NCI αl-α6 domains between the j83' and (84' strands, as discussed in more detail below. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula IX are useful for inhibiting hexamer interactions of type IV collagen.
In a preferred embodiment, the polypeptides of general formula IX are selected from the group consisting of AGAE (αl, α5, and α6) (SEQ ID NO:156), AGSE (α3) (SEQ ID NO:157), AGDE (o2) (SEQ ID NO:158), and AGDQ (α4) (SEQ ID NO:159).
In a further embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS:156-159 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: X1-AGAE-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VMHTS (SEQ ID NO: 160), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSGQA (SEQ ID NO: 161) (the full length sequence would thus be VMHTSAGAEGSGQA) (SEQ ID NO: 162); cθ: X3-AGSE-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMFTS (SEQ ID NO: 163), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GTGQA (SEQ ID NO: 164) (the full length sequence would thus be IMFTSAGSEGTGQA) (SEQ ID NO:165); α5: X5-AGAE-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence MMHTS (SEQ ID NO: 166), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSGQA (SEQ ID NO: 161) (the full length sequence would thus be MMHTSAGAEGSGQA) (SEQ ID NO: 167); α2: X2-AGDE-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTA (SEQ ID NO: 168), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQS (SEQ ID NO: 169) (the full length sequence would thus be LMHTAAGDEGGGQS) (SEQ ID NO: 170); α4: X4-AGDQ-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTG (SEQ ID NO: 171), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQA (SEQ ID NO: 172) (the full length sequence would thus be LMHTGAGDQGGGQA) (SEQ ID NO: 173); and aβ: X6-AGAE-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTA (SEQ ID NO:168), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQS (SEQ ID NO: 169) (the full length sequence would thus be LMHTAAGAEGGGQS) (SEQ ID NO: 174).
In a further embodiment wherein the polypeptides comprise sequences present at the hexamer interface, as determined from the deduced crystal structure, the polypeptides of the invention consist of at least 5 amino acids of the sequence of general formula X: EC(R1)G(R2)(R3)GTC(R4)(R5)(R6) (SEQ ID NO:175) wherein RI is selected from the group consisting of H, N, Q, and S;
R2 is selected from the group consisting of G, R, A, or is absent;
R3 is selected from the group consisting of R and Q
R4 is selected from the group consisting of N and H; R5 is selected from the group consisting of F and Y; and
R6 is selected from the group consisting of F and Y.
In various preferred embodiments, the polypeptide consists of at least 6, 7, 8, 9, 10, 11, or 12 amino acids of general formula X. In a preferred embodiment, the polypeptide consists of 12 amino acids of general formula X. This general formula X extensively overlaps with the Intra-CDSR, discussed above, and is present within the βό'-βl' strands, as discussed in more detail below. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula X are useful for inhibiting hexamer interactions of type IV collagen.
In a further embodiment, the polypeptides are as described above for general formula X, with the exception that R2 is selected from the group consisting of G, R, A; and R4 is H. Polypeptides of this embodiment are derived from the consensus sequence of the α2/4/6 of general formula X. h a further preferred embodiment, the polypeptides of general formula X are selected from the group consisting of ECHGRGTCNYY (αl/3/5) (SEQ ID NO:176), ECNGGRGTCHYY (o2) (SEQ ID NO:177), ECQGRQGTCHFF (α4) (SEQ ID NO:178), and ECSGARGTCHYF (α6) (SEQ ID NO:179).
In a further preferred embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula XI: (R1)(R2)T(R3)K (SEQ ID NO:180) wherein RI is selected from the group consisting of P, S, and A; R2 is selected from the group consisting of S, E, and D; and R3 is selected from the group consisting of L and V.
This general formula XI is present overlapping with the (89' strand in the crystal structure, as discussed in more detail below. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula XI are useful for inhibiting hexamer interactions of type IV collagen. hi a preferred embodiment of general formula XI, R3 is L (as in 02/4/6/1/5). In a further preferred embodiment of general formula XI, R2 is selected from D and E (oQ/4/5/6). In further preferred embodiments, the polypeptide according to general formula XI is selected from the group consisting of PSTLK (αl) (SEQ ID NO:181), PSTVK (oβ) (SEQ ID NO:182), SETLK (α5 and α6) (SEQ ID NO:183), ADTLK (α2) (SEQ ID NO:184), and PDTLK (α4) (SEQ ID NO:185).
In a further embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS:181-185 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: X1-PSTLK-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FKKPT (SEQ ID NO: 186), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGELR (SEQ ID NO: 187) (the full length sequence would thus be FKKPTPSTLKAGELR) (SEQ ID NO: 188); cθ: X3-PSTVK-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FRKPI (SEQ ID NO: 189), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGELE (SEQ ID NO: 190) (the full length sequence would thus be
FRKPIPSTVKAGELE) (SEQ ID NO:191); α5: X5-SETLK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FSKPQ (SEQ ID NO:192), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGDLR (SEQ ID NO: 193) (the full length sequence would thus be
FSKPQSETLKAGDLR) (SEQ ID NO: 194); α2: X2-ADTLK-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QGSPS (SEQ ID NO:195), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGLIR (SEQ ID NO: 196) (the full length sequence would thus be QGSPSADTLKAGLIR) (SEQ ID NO: 197); α4: X4-PDTLK-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SSAPA (SEQ ID NO:198), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ESQAQ (SEQ ID NO:199) (the full length sequence would thus be
SSAPAPDTLKESQAQ) (SEQ ID NO: 200); and α6: X6-SETLK-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GELPV (SEQ ID NO:201), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGQLH (SEQ ID NO:202) (the full length sequence would thus be
GELPVSETLKAGQLH) (SEQ ID NO: 203). In a further preferred embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula XII:
A(R1)RND (SEQ ID NO:204) wherein RI is selected from the group consisting of S, Q, and R. This general formula XII is present in the highly conserved loop connecting the β7 and β8 strands in the crystal structure. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula XII are useful for inhibiting hexamer interactions of type IV collagen.
In further preferred embodiments, the polypeptide according to general formula XII is selected from the group consisting of ASRND (αl, α3, α5, α2) (SEQ ID NO:205), AQRND (α4) (SEQ ID NO:206), and ARRND (α6) (SEQ ID NO-.207).
In a further embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS:205, 206, and 207 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl and α5: Xl-ASRND-Zl, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence NVCNF (SEQ ID NO: 208), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSYWL (SEQ ID NO: 209) (the full length sequence would thus be NVCNFASRND YSYWL) (SEQ ID NO: 210); α3: X3-ASRND-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence DVCNF (SEQ ID NO: 211), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSYWL (SEQ ID NO: 209) (the full length sequence would thus be DVCNFASRNDYSYWL) (SEQ ID NO:212); α2: X2-ASRND-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence DVCYY (SEQ ID NO:213), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KSYWL (SEQ ID NO:214) (the full length sequence would thus be DVCYYASRNDKSYWL) (SEQ ID NO: 215); α4: X4-AQRND-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QVCHY (SEQ ID NO:216), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RSYWL (SEQ ID NO:217) (the full length sequence would thus be QVCHYAQRNDRSYWL) (SEQ ID NO: 218); and α6: X6-ARRND-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence EVCHY (SEQ ID NO:219), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KSYWL (SEQ ID NO:214) (the full length sequence would thus be EVCHYARRNDKSYWL) (SEQ ID NO: 220).
In a further preferred embodiment, the polypeptides of the invention consist of an amino acid sequence of general formula XITI:
(R1)(R2)(R3)N(R4) (SEQ ID NO:221) wherein RI is selected from the group consisting of Y and F;
R2 is selected from the group consisting of Y and F;
R3 is selected from the group consisting of A and S; and
R4 is selected from the group consisting of A, S, and K.
This general formula XIII is present in the highly conserved loop connecting the β7' and β8' strands in the crystal structure. This region is present at the hexamer interface, and is involved in hexamer assembly and stabilization. As such, peptides of general formula XIII are useful for inhibiting hexamer interactions of type IV collagen.
In further preferred embodiments, the polypeptide according to general formula XIII is selected from the group consisting of YYANA (αl) (SEQ ID
NO:222) YYSNS (α3) (SEQ ID NO:223) YYANS (α5) (SEQ ID NO:224) YYANK
(α2) (SEQ ID NO:225) FFANK (α4) (SEQ ID NO:226) and YFANK(α6) (SEQ ID
NO:227).
In a further embodiment, the hexamer polypeptides selected from the group consisting of SEQ ID NOS:222-227 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: X1-YYANA-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229) (the full length sequence would thus be RGTCNYYANAYSFWL) (SEQ ID NO: 230); α3: X3-YYSNS-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229) (the full length sequence would thus be RGTCNYYSNSYSFWL) (SEQ ID NO:231); α5: X1-YYANS-Z2, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229) (the full length sequence would thus be RGTCNYYANSYSFWL) (SEQ ID NO: 232); α2: X2-YYANK-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCH (SEQ ID NO:233), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229) (the full length sequence would thus be RGTCHYYANKYSFWL) (SEQ ID NO: 234); α4: X4-FFANK-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QGTCH (SEQ ID NO:235), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229) (the full length sequence would thus be QGTCHFFANKYSFWL) (SEQ ID NO: 236); and o6: X6-YFANK-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCH (SEQ ID NO:233), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229) (the full length sequence would thus be RGTCHYFANKYSFWL) (SEQ ID NO: 237).
In a further embodiment, the present invention provides novel polypeptides derived from the hypervariable region of the type IV collagen α chain NCI domain sequences located between the (88'and the /39' strands, which are identified from the crystal structure as being present at the monomer-monomer interface, and which include the SRP and are involved in providing appropriate secondary structure for optimal interactions between the SR and the SRP. In this embodiment, the polypeptides consist of at least 7 amino acids of a sequence selected from the group consisting of lERSEMFKKPT (αl) (SEQ ID NO:238), LNPERMFRKPI (α3) (SEQ ID NO:239), VDVSDMFSKPQ (cό) (SEQ ID NO:240), TPEQSFQGSPS (α2) (SEQ ID NO:241), VKADLQFSSAPA (α4) (SEQ ID NO:242), and VEERQQFGELPV (aβ) (SEQ ID NO:243). In various embodiments, the polypeptides consist of at least 8, 9, 10, 11, or 12 amino acids of a sequence selected from the group consisting of SEQ ID NO:235-240. h a further embodiment, the polypeptides selected from the group consisting of SEQ ID NOS:238-243 may optionally further include 0-5 amino acids at either or both the amino and carboxyl terminus that are derived from the same α chain, in order to provide appropriate secondary structural characteristics to the polypeptide for optimal inhibitory activity. Such polypeptides can thus be selected from the group consisting of: αl: X1-IERSEMFKKPT-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAT (SEQ ID NO: 244), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PSTLK (SEQ ID NO: 181) (the full length sequence would thus be FWLATIERSEMFKKPTPSTLK) (SEQ ID NO: 245);
03: X3-LNPERMFRKPI-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAS (SEQ ID NO: 246), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PSTVK (SEQ ID NO: 182) (the full length sequence would thus be FWLASLNPERMFRKPIPSTVK) (SEQ ID NO:247); α5: X1-VDVSDMFSKPQ-Z2, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAT (SEQ ID NO: 244), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SETLK (SEQ ID NO: 183) (the full length sequence would thus be FWLATVDVSDMFSKPQSETLK) (SEQ ID NO: 248); α2: X2-TPEQSFQGSPS-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ADTLK (SEQ ID NO: 184) (the full length sequence would thus be FWLTTIPEQSFQGSPSADTLK) (SEQ ID NO: 250); α4: X4-VKADLQFSSAPA-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PDTLK (SEQ ID NO: 185) (the full length sequence would thus be FWLTT VKADLQFS SAP APDTLK) (SEQ ID NO: 251); and α6: X6-VEERQQFGELPV-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SETLK (SEQ ID NO: 183) (the full length sequence would thus be FWLTTVEERQQFGELPVSETLK) (SEQ ID NO: 252). In further embodiments, the present invention provides other polypeptides that include multiple regions identified as being important for inhibiting monomer- monomer interactions (and thus heterotrimer assembly), and/or trimer-trimer interactions (and thus hexamer assembly). Polypeptides according to this aspect of the invention include the following:
SR plus the h ter-CDSR: αl FSTMPFLFCNINNVCNFA (SEQ ID NO: 253) α3 FTTMPFLFCNVNDVCNFA (SEQ ID NO: 254) α5 FSTMPFMFCNINNVCNFA (SEQ ID NO: 255) α2 FSTMPFLYCNPGDVCYYA (SEQ ID NO: 256) α4 FSTLPFAYCNIHQVCHYA (SEQ ID NO: 257) cώ FSTMPFIYCNlNEVCHYA (SEQ ID NO: 258)
hiter-CDSR plus contiguous hexamer interface region: αl PFLFCNΓNNVCNFASRND (SEQ ID NO: 259) o3 PFLFCNVNDVCNFASRND (SEQ ID NO: 260) α5 PFMFCNΓNNVCNFASRND (SEQ ID NO: 261) α2 PFLYCNPGDVCYYASRND (SEQ ID NO: 262) α4 PFAYCNIHQVCHYAQRND (SEQ ID NO: 263) α6 PFΓYCNΓNEVCHYARRND (SEQ ID NO: 264)
SR plus the Inter-CDSR plus contiguous hexamer interface region: αl FSTMPFLFCNTNNVCNFASRND (SEQ ID NO: 265) α3 FTTMPFLFCNVNDVCNFASRND (SEQ ID NO: 266) o5 FSTMPFMFCNINNVCNFASRND (SEQ ID NO: 267) α2 FSTMPFLYCNPGDVCYYASRND (SEQ ID NO: 268) α4 FSTLPFAYCNIHQVCHYAQRND (SEQ ID NO: 269) α6 FSTMPFΓYCNINEVCHYARRND (SEQ ID NO: 270)
Intra-CDSR plus contiguous hexamer interface region: aland o5: PFIECHGRGTCNYY (SEQ ID NO:271) α3 : PFLECHGRGTCNYY (SEQ ID NO: 272) α2: PFIECNGGRGTCHYY (SEQ ID NO: 273) α4: PFLECQGRQGTCHFF(SEQ ID NO: 274) α6: PFIECSGARGTCHYF (SEQ ID NO: 275)
SRP/variable region plus contiguous hexamer interface: αl IERSEMFKKPTPSTLKAG (SEQ ID NO: 276) o3 LNPERMFRKPΓPSTVKAG (SEQ ID NO:277) o5 VDVSDMFSKPQSETLKAG (SEQ ID NO: 278) α2 rPEQSFQGSPSADTLKAG (SEQ ID NO: 279) α4 VKADLQFSSAPAPDTLKES (SEQ ID NO: 280) α6 VEERQQFGELPVSETLKAG (SEQ ID NO: 281)
Specific monomer-monomer inhibitor plus SR: αl GSCLRKFSTM (SEQ ID NO: 282) α3 GSCLQRFTTM (SEQ ID NO:283) α5 GSCLRRFSTM (SEQ ID NO: 284) α2 GSCLARFSTM (SEQ ID NO: 285) α4 GSCLPVFSTL (SEQ ID NO: 286) α6 GSCLPRFSTM (SEQ ID NO: 287)
Monomer-monomer inhibitor plus SR plus hiter-CDSR plus hexamer interface αl LRKFSTMPFLFCNINNVCNF (SEQ ID NO: 288) LQRFTTMPFLFCNVNDVCNF (SEQ ID NO:289) LRRFSTMPFMFCNΓNNVCNF (SEQ ID NO: 290) LARFSTMPFLYCNPGDVCYY (SEQ ID NO: 291) LPVFSTLPFAYCNTHQVCHY (SEQ ID NO: 292) LPRFSTMPFIYCNiNEVCHY (SEQ ID NO: 293)
In another aspect, the present invention provides methods for inhibiting angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly, comprising administering to a subject in need thereof an amount effective to inliibit angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, endothelial cell adhesion and/or proliferation, and basal lamina assembly of one or more polypeptides of the invention, antibodies against such polypeptides, or pharmaceutical compositions thereof.
"Angiogenesis-mediated disorders" refers to diseases and conditions with accompanying undesired angiogenesis, including but not limited to solid and blood- borne tumors, diabetic retinopathy, rheumatoid arthritis, retinal neovascularization, choroidal neovascularization, macular degeneration, corneal neovascularization, retinopathy of prematurity, corneal graft rejection, neovascular glaucoma, retrolental fibroplasia, epidemic keratoconjunctivitis, Vitamin A deficiency, contact lens overwear, atopic keratitis, superior limbic keratitis, pterygium keratitis sicca, sogrens, acne rosacea, phylectenulosis, syphilis, Mycobacteria infections, lipid degeneration, chemical burns, bacterial ulcers, fungal ulcers, Herpes simplex infections, Herpes zoster infections, protozoan infections, Kaposi's sarcoma, Mooren ulcer, Terrien's marginal degeneration, marginal keratolysis, trauma, systemic lupus, polyarteritis, Wegeners sarcoidosis, scleritis, Steven's Johnson disease, radial keratotomy, sickle cell anemia, sarcoid, pseudoxanthoma elasticum, Pagets disease, vein occlusion, artery occlusion, carotid obstructive disease, chronic uveitis, chronic vitritis, Lyme's disease, Eales disease, Bechets disease, myopia, optic pits, Stargarts disease, pars planitis, chronic retinal detachment, hyperviscosity syndromes, toxoplasmosis, post- laser complications, abnormal proliferation of fibrovascular tissue, hemangiomas, Osler-Weber-Rendu, acquired immune deficiency syndrome, ocular neovascular disease, osteoarthritis, chronic inflammation, Crohn's disease, ulceritive colitis, psoriasis, atherosclerosis, and pemphigoid. (See U.S. Patent No. 5,712,291)
The polypeptides, or antibodies against such polypeptides, may be subjected to conventional pharmaceutical operations such as sterilization and/or may contain conventional adjuvants, such as preservatives, stabilizers, wetting agents, emulsifiers, buffers etc.
For administration, the polypeptides, or antibodies against such polypeptides, are ordinarily combined with one or more adjuvants appropriate for the indicated route of administration. The polypeptides, or antibodies against such polypeptides, may be admixed with lactose, sucrose, starch powder, cellulose esters of alkanoic acids, stearic acid, talc, magnesium stearate, magnesium oxide, sodium and calcium salts of phosphoric and sulphuric acids, acacia, gelatin, sodium alginate, polyvinylpyrrolidine, and/or polyvinyl alcohol, and tableted or encapsulated for conventional administration. Alternatively, the polypeptides, or antibodies against such polypeptides of this invention may be dissolved in saline, water, polyethylene glycol, propylene glycol, carboxymethyl cellulose colloidal solutions, ethanol, corn oil, peanut oil, cottonseed oil, sesame oil, tragacanth gum, and/or various buffers. Other adjuvants and modes of administration are well known in the pharmaceutical art. The carrier or diluent may include time delay material, such as glyceryl monostearate or glyceryl distearate alone or with a wax, or other materials well known in the art.
In practicing this aspect of the invention, the amount or dosage range of the polypeptides, antibodies against such polypeptides, or pharmaceutical compositions employed is one that effectively inhibits angiogenesis, angiogenesis-mediated disorders, tumor growth, tumor metastasis, and/or endothelial cell-extracellular matrix interactions. An inhibiting amount of the polypeptides that can be employed ranges generally between about 0.01 μg/kg body weight and about 10 mg/kg body weight, preferably ranging between about 0.05 μg/kg and about 5 mg/kg body weight. The polypeptides, antibodies against such polypeptides, or pharmaceutical compositions thereof may be administered by any suitable route, including orally, parentally, by inhalation spray, rectally, or topically in dosage unit formulations containing conventional pharmaceutically acceptable carriers, adjuvants, and vehicles. The term parenteral as used herein includes, subcutaneous, intravenous, intra-arterial, intramuscular, intrasternal, intratendinous, intraspinal, intracranial, intrathoracic, infusion techniques or intraperitoneally. In preferred embodiments, the polypeptides are administered intravenously or subcutaneously.
The polypeptides, antibodies against such polypeptides, or pharmaceutical compositions thereof may be made up in a solid form (including granules, powders or suppositories) or in a liquid form (e.g., solutions, suspensions, or emulsions). The polypeptides and antibodies against such polypeptides of the invention may be applied in a variety of solutions. Suitable solutions for use in accordance with the invention are sterile, dissolve sufficient amounts of the polypeptides, and are not harmful for the proposed application. In a preferred embodiment, one or more of the disclosed polypeptides, antibodies against such polypeptides, or pharmaceutical compositions thereof, are used so as to target more than one region of type IV collagen for inhibition of assembly.
For example, peptides that target different hexamer regions can be used in combination to increase their inhibitory effect. Alternatively, or additionally, combining a peptide targeting monomer-monomer interactions with a peptide that targets hexamer assembly can provide an additive inhibitory effect. Other combinations are well within the knowledge of one of skill in the art, based on the teachings herein.
EXAMPLES
Protein Purification and Crystallization. The [(αl)2.α2]2 NCI hexamer was isolated from bovine eye lenses purchased from Pel-Freeze Biologicals (Rogers, AR) (37). Briefly, LBM was prepared by sonication of the lenses in the presence of 1 M NaCl and protease inhibitors (38). To cleave the NCI domain from the full-length type IN collagen, the LBM preparation was digested with bacterial collagenase at 37° C. The ΝC1 hexamer was purified by using DE-52 and S-300 column chromatography.
Initial crystallization screening with commercial sparse matrix kits (Hampton Research, Laguna Νiguel, CA) was carried out using concentrated protein (10 mg/ml) and hanging drop vapor diffusion method. LBM ΝC1 crystals grow as small clusters overnight in 10% (w/v) PEG 20K, 0.1 M Bicine buffer (pH 9.0) at room temperature. Diffraction quality crystals were grown using microseeding procedures under similar conditions with lower protein concentration. The crystals belong to monoclinic P2\ space group with unit cell dimensions a = 129.41 A, b = 143.87 A, c = 162.92 A, and β = 91.3° at room temperature and four hexamers in the asymmetric unit. Cryocooling of the crystals in 25% 2,4-methyl pentanediol (MPD) or glycerol results in the shrinkage of the unit cell (a = 127.16 A, b = 139.57A; c = 160.20 A; β= 91.3°).
Structure Determination and Refinement. Initial heavy atom soaks were carried out at the crystallization pH and later switched to neutral pH with phosphate buffer. ΝC1 crystals soaked in synthetic mother liquor containing 2mM LuCl or K2PtCl6 transform the lattice to a smaller unit cell of dimensions a - 79.79 A, b = 137.20 A, c = 126.69 A, β = 90.3° and two hexamers in the asymmetric unit. The crystals were routinely transformed into new form by soaking in 2 mM LuCl3 overnight and used for further heavy atom soakings. Multiwavelength anomalous diffraction (MAD) data sets were collected at peak, inflection and two remote wavelengths using a single crystal soaked in 0.5 M KBr for 1 min and flash-frozen in cold Ν2 stream (Table 1). The heavy atom soak screens were carried out at beamlines 1-5 and 9-2 of Stanford Syncrhortron Radiation Laboratory (SSRL) and beamline X8C of National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. The Br-MAD data sets used in this study were collected at SSRL and processed using DENZO and SCALEPACK programs of HKL2000 suite (39). The Br" sites were located using SOLVE program (40) and 37 highest peaks (> 6σ) were used for phasing the reflections at 2.2 A resolution. The resulting phases were improved by solvent flattening using RESOLVE (41) and the electron density map was calculated using FFT program of CCP4 suite (42). Polypeptides of two αl chains and one α2 chain (chains A-C) were traced using the TOM FRODO graphics program (43). The complete asymmetric unit was generated using non-crystallographic symmetry ("NCS") relations obtained from Br" sites — first the second trimer (chains D-F) was generated to complete one hexamer and then the second hexamer (chains G-L) was generated from the first hexamer. The 2.0 A data set collected at 0.8856 A (λ ) was used for model refinement using CNS program (44) and 5% of the data were set aside for monitoring Rfree. The initial model was subjected to rigid body refinement using reflections in the 30.0-3.0 A resolution range (R = 0.361 and Rfree = 0.364 ) followed by simulated annealing refinement in the 10.0-2.5 A resolution range (R = 0.326 and Rfree = 0287). Resolution was slowly extended to 2.0 A in several iterative cycles of model building and refinement of positional and thermal parameters. During the final rounds of refinement, solvent molecules (water and glycerol) and Br" ions were added in steps using 2F0-FC and F0-Fc maps and hydrogen bonding criteria. Multiple conformers of a few sidechains were modeled in the final round. The structure was analyzed using SETOR(45), GRASP(46), and SURFNET(47) graphics software packages and various utility programs in CCP4 suite. The hexamer interface was analyzed using HBPLUS(48) and protein-protein interaction web server (http://www.biochem.ucl.ac.uk/bsm/ PP/server/). Table 1. Summary of Crystallographic Analysis
Data Collection
Dataset Peak Inflection Remote 1 Remote2
Wavelength (A) 0.9195 0.9197 0.9537 0.8856
Resolution (A) 2.1 2.1 2.15 2.0
Measured reflections 602,172 603,309 568,640 686,286
Unique reflections 159,617 159,667 149,817 184,445
Completeness (%) 98.3 (90.9) 98.2 (90.5) 98.7 (95.1) 97.9 (87.8)
Rsym(%)t 4.0 (7.7) 3.0 (6.7) 2.4 (4.9) 3.4 (8.6)
I/σ(I) 29.2(15.0) 33.0 (18.2) 37.6 (26) 30.5 (13.1)
Phasing Statistics
Resolution range (A) 50.0 - 2.2
Number of Br sites 33
Overall Z-score 127
Figure of Merit 0.67 / 0.76 SOLVE / RESOLVE
Refinement Statistics
Resolution range (A) 8.0 - 2.0
Number of reflections (σ>2) 166,448 / 8,789 working / test
R;ryst/ Rfree (%) 17.0 / 19.6
RMS deviation
Bond lengths (A) 0.0051
Bond angles (°) 1.29
The overall completeness is given, with the completeness in the highest resolution shell shown in the parentheses. Similar convention in is followed for Rsym and I/σ(I) also. ^Rsym = ∑h∑; | I(h)> - I(h);| / ∑h∑i|l(h)i|. * 5% of the data were excluded from refinement and were used to determine the Rϋee. The Rcryst does not include these reflections. In both cases R=∑( \ F0\ - k\ C|)/∑| 0|, with an appropriate choice of reflections for the summation.
RESULTS AND DISCUSSION
Structure Determination and Overview. The bovine LBM NCI hexamer, composed of αl and α2 chains, crystallizes in monoclinic space group P2\ (A-form) with four hexamers per asymmetric unit. This is different from the crystal forms reported for mouse EHS tumor NCI (49) and human placenta NCI hexamers (50), which crystallized with two hexamers and one hexamer in the asymmetric unit respectively. The intensity statistics of the preliminary diffraction data suggested the presence of pseudo-translation symmetry along the c axis in LBM NCI crystals. An extensive search for heavy atom derivatives using soaking experiments was not successful. However, crystals soaked in LuCl3 at pH 7.0 transformed the lattice to a smaller unit cell as a result of pseudo-translation symmetry becoming crystallographic translation in the same space group with only two hexamers in the asymmetric unit (B-form). MAD data of the crystals soaked in LuCl3 did not provide useful phase information, probably due to a single weak binding site that was responsible for lattice transformation. However, we took advantage of the smaller unit cell for further heavy atom screening, including the newly suggested short-soaking strategy with halides (51,52). The LuCl -soaked B-form crystal structure was determined at 2.0 A resolution by the MAD method using Br" as the anomalous scatterer combined with solvent flattening. The data collection, phasing and refinement statistics are shown in Table 1.
The map was fitted with human NCI αl and α2 sequences (Fig. 2) since neither of the bovine sequences is available. Four each of the αl and α2 sequences of other mammalian species are known, which share more than 95% sequence identity among them. More than 95% of the residues of the human sequences fit experimental electron density map. Differences between the human sequences and the map were found for residues ιlel5Thr, Ser22Pro, Prol29Gln in αl chain and Asp96Glu, Glu97Asp, and Gly 176 Ala in α2 chain. The sequences are numbered so that the residue after the last Gly-Xaa-Yaa repeat of the collagenous region is counted as the first residue in both α chains. The 12 chains in two hexamers have been assigned chain IDs A-L in the order of αl, αl and α2 in each trimer. The map shows disorder for 5-6 residues at N- and two residues at C-termini of all the chains. The final model includes two hexamers, 36 Br" ions, 48 glycerol molecules and 1139 water molecules. The final R-factor and Rfree of the refinement are 0.168 and 0.197 respectively. More than 90%ι of the residues are within the most favorable regions in Ramachandran map and Arg76 and Serl48 of the first αl chain, Serl48 of the second αl chain and Arg75, Glu95 and Alal45 of α2 chain in each trimer lie in the disallowed region. Only a handful of residues are in multiple conformations. The two hexamers in the asymmetric unit are similar with no apparent differences due to crystal contacts. The hexamer comprising chains A-F is used to describe the model.
The overall structure of the hexamer is illustrated in Fig. 3. The two trimers in the hexamer are related by a 2-fold NCS axis at the interface ("equatorial plane") and the monomers within a trimer are related by a pseudo 3 -fold symmetry coinciding with the triple helix axis ("polar axis").
Monomer Topology: The NCI monomer folds into a novel tertiary structure with predominantly β-strands as predicted by our earlier study using multiple sequence alignment (22)(Fig. 4). The two αl chains in the trimer are identical and the α2 chain has a similar overall structure. The Cα atoms of 214 matching residues in one of the αl chains and the α2 chain superimpose with an RMS deviation of 0.9 A. Each chain can be divided into two homologous subdomains, N- and C-subdomains. The two subdomains fold in a similar topology and Cα atoms of 96 matching residues of two subdomains of αl chain superimpose with an RMS deviation of 1.0 A. The 12 invariant cysteine residues form six disulfides, three in each subdomain, at conserved positions (Fig. 2 and 5). The major difference between the two subdomains occurs at the regions encompassing Pro86-Pro95 in the N-subdomain and Hel96-Thr209 in the C-subdomain, which are least conserved in the six human sequences (Fig. 1). Each subdomain has two β-sheets — a three-strand anti-parallel sheet (I & I') close to the triple helical junction and a six-strand anti-parallel sheet (II & IF) close to the hexamer interface, which consists of the regions of interactions between the two trimers that make up the hexamer (Fig. 4and 5). The β-sheet I is formed by the three non-contiguous strands (βl, βlO and β2) of the sequence belonging to the first half of the polypeptide. However, in the β-sheet π, only four strands (β4, β3, β8, and β9) belong to the first half of the sequence and the remaining two strands (β6' and β7') form a part of the second half of the sequence. Thus, a β-hairpin structure from the second half of the sequence (the "infra-chain domain swapping region", or "Intra- CDSR") swaps into the N-subdomain to form a six-strand β-sheet. The two halves of the polypeptide being topologically similar, the region in the C-subdomain corresponding to the six-strand β-sheet in the N-subdomain lacks two strands to form a similar β-sheet in the isolated monomer structure. Similarly, β6-β7 hairpin in the
N-terminal half, which corresponds to the β6'-β7' hairpin in the C-terminal involved in the domain swapping interaction, extends out in the monomer structure. These two features form the basis for the trimer organization described in the next section.
Trimer Organization: Two chains of the αl NCI domain and one chain of the α2 NCI domain form the trimer structure with a pseudo 3 -fold molecular symmetry. Since each chain is made up of topologically similar subdomains, there is even a pseudo 6-fold symmetry. The topology diagram of the trimer is shown in Fig. 5. The trimer structure is approximately cone-shaped with a base diameter of about 65 A and a hollow core of about 12-14.0 A inner diameter. This is about the same of as the diameter of the collagen triple helix, with N-termini of all three chains coming together at the vertex of the cone where the triple helical collagenous domain links with the NCI domain. The trimer is tightly packed through several interchain hydrophobic and hydrogen bonding interactions (Table 2). Residues of five segments in the N-subdomain of one chain make contact with those of seven segments in the C- subdomain of the second chain, and constitute the "monomer-monomer interface", which consists of the regions of monomer-monomer interaction within the trimer. The most important interactions are confined to one N-subdomain segment and two C- subdomain segments (Fig. 1). There are two levels of monomer-monomer interactions, one essential for the "generic trimer" assembly and the other dictating the oNCl chain specificity of the monomer-monomer interactions within the trimer.
Table 2. Comparison of monomer-monomer interfaces in the trimer. αlA-αlB αlb-α2 α2-αlA
Interface Parameter αlA αlB αlB α2 2 αlA
Number of segments 5 7 5 7 5 8 Number of residues 49 60 51 65 49 59 Δ ASA (A2) 2137 2182 2087 2066 1985 2044 Polar/non-polar atoms 40.1/59.9 24.5/75.5 44.3/55.7 32.5/67.5 39.9/60.1 24.8/75.3
Hydrogen bonds
M-M/M-S/S-S 9/8/5 11/8/12 9/9/3
Δ ASA, interface solvent accessible area; M, main chain; S, side chain Within the trimer, the following monomer-monomer interfaces exist: αlA- o2C; αlB-α2C;and αl A-αlB. The hexamer contains two such trimers; the monomer- monomer interfaces in the second trimer are αlD-α2F; αlE-α2F;and αlD-αlE.
Generic Trimer: At the first level, the monomers intertwine with each other to form the trimer through 3D domain swapping interactions (Fig. 5 and 6a) (53). A six- strand β-sheet (IF) is formed in the C-subdomain from strands of two different α chains similar to the β-sheet II in the N-subdomain formed from the strands in two halves of the same chain. These β-sheets are indistinguishable in αl and α2 chains. Thus, there are six β-sheets (II/IF), one in each of the six subdomains, forming the close-ended 3D domain swapping interactions in the NCI trimer structure. Each of these six-strand β-sheets is formed by four strands (β4/4', β3/3', β8/8', β9/9') in one half of the sequence and the remaining two strands (β676, β777) are contributed by the other half of the same chain (ββ/βl; the Inter-CDSR) or adjacent chain (/36V/37/; the "fritra-chain domain swapping region", or "Intra-CDSR"). The amino acid sequences of all the strands with the exception of β9, are highly conserved in α chains within and across the species. The six topologically similar β-sheets formed in cyclical fashion give the pseudo 6-fold symmetry appearance for the trimer (Fig. 6a). In each of the β-sheets, the outermost strand (β9//39') lies on the surface parallel to the equatorial plane of the hexamer interface forming a part of the outer ring and the innermost strand (β4/β4') runs nearly parallel to the polar axis or pseudo 3 -fold axis in the core. The angle between these two strands within each sheet is about 75° giving it a right-handed twist. The β4/β4' strands from all the six β-sheets form a parallel β barrel-like core of about 14 A diameter even though there are no backbone hydrogen bonds between them (Fig. 6a). However, these core strands are stabilized by backbone-side chain hydrogen bonds either directly or mediated through solvent molecules. The β4/4' strands have a mixture of hydrophobic and hydrophilic residues, with the former pointing to the core and the latter pointing towards the adjacent strand. Interestingly, the β4 strands contain long chain hydrophilic amino acids so that they form more direct hydrogen bonds with the backbone atoms of the β4' strand of the neighboring chain indicating stronger interchain interactions. The interactions between β4' and β4 within a chain are mainly mediated through solvent molecules. Thus, the six-strand β-sheets are essential structural components in the organization of the generic trimer structure through 3D domain swapping interactions and the compact β barrel-like core structure. However, they may play only a limited role in the chain specific assembly of the trimer. Therefore, compounds that target the Intra-CDSR, the hiter-CDSR, and the /34//34' based β barrel-like core, such as peptides derived from these regions, can be used to inhibit generic monomer-monomer interactions, and thus to inhibit trimer assembly.
Chain Specificity in the Trimer Structure: The sequence of the loop connecting the β8' and β9' strands is the most variable region in all the six human α chains (referred to as the "hypervariable region"). This hypervariability in the primary sequences manifests itself as different secondary structures in the αl and α2 chains in the crystal structure. Whereas it forms a short 310 helix (g2') in all the αl-like chains (the "specificity region partner" or "SRP"; Glu200-Lys204 (EMFKK)), the corresponding region in α2 chain (Serl98-Gln200; SFQ) adopts an extended conformation (βp') and pairs with the extended structure (the "specificity region", or "SR"; βp, Phe57-Met60; FSTM) in the adjacent αlB chain to form a short parallel β-sheet (Fig. 8b). It should be noted that the sequence of the SR from αl and α2 is identical (FSTM). This is the only parallel β-sheet in the entire structure, which is predominantly made up of β-strands. The sequence of the βp is highly conserved in all the six α chains and forms the same extended structure in α2 chain also, even though it doesn't have a partner in αlA chain to form the parallel β-sheet. Thus, these additional main chain hydrogen bond interactions between the two chains are found only at the αlB-α2 interface (i.e.: which includes the interaction of the SR of αl and the SRP of α2), but not in α2-αlA (i.e.: which includes the interaction of the SRP of αl and the SR of α2) or αlA-αlB (i.e.: which includes the interaction of the SR of αl and the SRP of αl) interfaces, due to the presence of the 310 helical structure in αl chains rather than the extended structure present in α2 chain. Besides tins difference in the secondary structural elements in the three interfaces, there are also differences in the main chain-side chain and side chain-side chain interactions at the monomer-monomer interface (Fig. 6b). This is also reflected in different ratios of polar to non-polar atoms at the three interfaces (Table 2). Therefore, compounds that target the SR, the SRP, or the hyper-variability region, such as peptides derived from these regions, can be used to inhibit specific monomer-monomer interactions, and thus inhibit trimer assembly.
Furthermore, given the composition of the individual interfaces within the monomer-monomer interface, a preferred inhibitor of specific trimer assembly would target the SR, which is identical in αl and α2, and thus such an inhibitor would be expected to interfere with interactions at each interface within the monomer-monomer interface, and thus to inhibit trimer assembly. Also preferred would be an inhibitor that targets the α2 SRP, which is required for the additional H-bonding interactions seen at the αlB-α2 interface.
The side chain of Lys56(αlB) is sandwiched between the backbone of the loop preceding the parallel β-sheet in α2 chain and the contiguous bonds of backbone and side chain of Glnl20(α2). In this tightly locked position, Lys56(αlB) assumes a linear conformation to form two strong hydrogen bonds with the carbonyl of Ilel94(α2) and the carboxyl of Aspl21(α2), and two more weak interactions with the carbonyls of Glnl20(α2) and Glul96(α2). The αl-like (ie: αl/3/5 family) region corresponding to the parallel β-sheet of α2 chain is the 310 helix, which spans a longer sequence. Hence, in the αlA-αlB interface, Lys56(αlA) is not quite parallel to the backbone bonds, which provides more room for this lysine to adopt a different rotamer conformation to form only weak hydrogen bond with the carbonyl oxygen of Ilel96(αlB). This may also be influenced by the presence of hydrophobic Thrl24 in αl chains in place of hydrophilic Aspl21 in α2. At the α2-αl A interface Arg55(α2) is docked in similar position as Lys56 of αl chains in other two interfaces with one strong hydrogen bond interaction with carbonyl of Ilel96(αl A). Other differences in amino acid sequences including Arg55/Ala54 and Gly98/Glu95 make differences in hydrogen bonding patterns at the interfaces. Thus, the Arg55(o2)/Lys56(αl) is an important residue for optimal αl-α2monomer-monomer interactions, and compounds targeting this region, such as peptides including LRKF (SEQ ID NO:294) (αl) or LARF (SEQ ID NO:295) (G2), can be used to inhibit the assembly of specific monomer-monomer interactions. Since this region precedes the SR, this region can be combined with the SR to form a longer peptide that will interfere with multiple aspects of specific monomer-monomer interactions, and thus be even more effective at inhibiting trimer assembly. Furthermore, the regions Ilel94-Glul96 (α2), Ilel96 (αl) and Glnl20- Aspl21(α2) also are involved in optimal αl-α2monomer-monomer interactions, and compounds targeting these region, such as peptides including IPE (SEQ ID NO:294) (α2 184-196), IER (SEQ ID NO:295) (αl 196-198) or QD (SEQ ID NO:296) (α2 120-121), can be used to inhibit the assembly of specific monomer-monomer interactions, and thus to inliibit trimer assembly.
The αlB-α2 interface (i.e.: which includes the interaction of the SR of αl and the SRP of α2) has the maximum number of contact residues, the highest proportion of hydrophilic atoms, and contains more hydrogen bonds than the other monomer- monomer interfaces (Table 2). On the other hand, the buried surface area is largest for αlA-αlB interface (i.e.: which includes the interaction of the SR of αl and the SRP of αl). From these observations, it is evident that the αlB-α2 interface is formed predominantly through hydrogen bonding interactions and the αlA-αlB interface is stabilized by more hydrophobic forces. In addition to the specific interactions at the interfaces, packing considerations may also play an important role in determining chain stochiometry in the trimer. Even though the αl and α2 NCI chains fold in a similar tertiary structure with a low RMS deviation, the relative orientation of the two subdomains in each NCI chain is different near the triple helical junction. The region encompassing Thrl3-Tyr30 of the N-subdomain in the α2 chain is farther from its equivalent region Aspl21-Tyrl38 of the C-subdomain in the α2 chain compared to the relative orientations of similar regions in the αl structure. The larger width of the α2 structure near the triple helical junction results in serious steric clashes when packed into a hypothetical α2- homotrimer. However, it is possible to accommodate three αl chains in a hypothetical homotrimer, albeit with weaker interactions.
It is preferred that peptides designed to interfere with monomer-monomer interactions are preferably delivered into the cell, where such monomer-monomer assembly occurs. Alternatively, the peptides can be used to disrupt assembled trimers that have been secreted by the cell.
Hexamer Assembly: The type IV collagen trimer, once formed in the endoplasmic lumen, is secreted into the extracellular space where it assembles into the hexamer, and then into a supramolecular network tlirough N- and C-terminal associations. The NCI domains play the dominant role in this assembly, by determining the C-terminal dimeric association, leading to hexamer assembly. In this section we describe the forces that influence such hexamer assembly as observed in the crystal structure, and provide a rationale for the specificity in the type IV collagen network assembly. The foot-ball shaped hexamer is made up of two identical trimers, each containing two αl chains and one α2 chain as described in the previous section. Each protomer (ie: the complete type IN collagen trimer, including ΝC1 domains) formed by the tightly intertwined trimer is considered as a single entity so that the hexamer can be analyzed relative to other homodimeric protein complexes (43). We have determined several parameters defining the hexamer interface to evaluate the strength of interactions between the two trimers and analyze hexamer assembly in the type IV collagen network (Table 3).
Table 3. Comparison of interface parameters defining the trimer-trimer interaction in the ΝC1 hexamer and observed mean for 32 homodimer complexes.
Interface Parameter ΝC1 Hexamer Observed Mean (43) (32 Homodimers)
ΔASA (A2) 4173.1 1685.03
Planarity 1.91 3.46
Circularity 0.87 0.71
Segmentation 18 5.22
Hydrogen bonds per 100 A2 1.2 0.70
Gap Index 1.24 2.2 Percentage of polar and non-polar atoms are 45.5 and 54.5 respectively.
Like most homodimers, the two ΝC1 trimers are related by a 2-fold ΝCS axis in lying the equatorial plane and perpendicular to the pseduo 3-fold axis of symmetry within an individual trimer (Fig. 4). This symmetry constraint may be partly influenced by a few differences in the interface residues of αl like and α2 like sequences in addition to more efficient packing. The hexamer interface is formed by the nearly flat surfaces of the two trimers, with an RMS deviation of 1.9 A for all the hexamer interface atoms from the mean plane (Fig. 9a). This is significantly lower than the average planarity value of 3.5 A for 32 homodimers discussed in a recent review (43). The hexamer interface formed by six segments each of the three monomers, with a total of 109 residues per trimer, is nearly circular, with the major and minor axial lengths of the mean plane measuring approximately 69 and 61 A respectively. This flat circular hexamer interface covers about 4400 A2 of solvent accessible area per trimer, which correlates with the observation of larger molecules having larger interfaces (54). Such a large interface facilitates strong interaction between the trimers, involving both hydrophobic and hydrophilic residues. The polar (45.5%) and non-polar atoms (54.5%) in the hexamer interface are nearly in equal proportions, underscoring the importance of both types of interactions in hexamer stabilization. The discussion thus far focused on the overall nature of the hexamer interface.
Next, the interactions between the individual chains at the hexamer interface are analyzed in more detail. Each monomer of one trimer makes contact with two monomers of the other trimer, designated as the "major" and "minor" contacts based on the extent of the contact area and number of hydrogen bonds. The two monomers making major contact is referred to as "dimer" in a similar sense as the term used in the denaturation experiments of hexamers (55). The 2-fold NCS between the two trimers results in only one "homodimer" formed by two αl chains (Figure 7A), with the remaining two "heterodimers" formed by αl and α2 chains (Figure 7A-B).
A 120° rotation of one trimer with respect to the other about the pseudo 3 -fold axis will result in an "all homodimers" structure. Why such an arrangement is not possible can be explained mainly on symmetry consideration: breaking the symmetry results in less efficient packing with possibly fewer interactions and some unfavorable contacts. In order to understand the complex hydrogen bonding interactions at the interface, it is essential to look into the interactions of each monomer with its "major" and "minor" interacting partners. The complexity presented even at this level may be simplified further by breaking down the interactions to three regions in the structure: "core" and "outer" regions of "major" contact and the "major-minor junction".
Core regions of major contact: The two 6-strand β-sheets, II and IF, formed by the 3D domain swapping interactions play as crucial role in the formation of hexamer assembly as in the case of trimer organization. The hexamer interface is populated with β-turns coi ecting β3-/34 and β3'-β4' in the core. These turns along with the remaining strands of the β-sheets 11/11' position a large number of conserved residues for extensive hydrogen bonding interactions at the hexamer interface. The core β-turns (two per monomer contributed by the two equivalent subdomains) in the two trimers pack in staggered configuration such that each turn in one trimer contacts with two turns in the other trimer. The turns in the N-subdomains are of type I'/III' containing hydrophilic amino acids in the second (Asn39/Gbι38) and third positions (Glu40/39). The C-subdomain turns are of type II in αl chains and type IF in α2 chains with small hydrophobic amino acids, Alal49/146-Glyl 50/147- Alal 51/Aspl48, with Alal 49 αl or Aspl48 of α2 introducing a β-bulge. Thus, the hydrophilic side chains of turns in the N-subdomain participate in hydrogen bonds and hydrophobic residues of turns in C-subdomain pack through hydrophobic interaction as well as stacking interaction of peptide planes (Fig. 7A). Whereas the Asn39(Gln38) side chain in the N-subdomain forms a hydrogen bond with the backbone amide in C- subdomain turn, the conserved Glu40(39) penetrates between the N- and C- subdomains of a monomer chain in the other trimer to form a hydrogen bond with the side chain of the conserved Gln37(36). The Glu40 residues in the αl-αl dimer form a strong hydrogen bond with each other that is missing in αl-α2 dimers. The packing of the turns and side chains appear to be tight at the core interface in CPK models indicating strong van der Waals interactions in additions to the obvious hydrogen bonding interactions. Therefore, compounds that target the core regions of major contact at the hexamer interface, such as peptides derived from these regions, can be used to inhibit hexamer assembly. For example, peptides including the β3-βA connecting region or the j83'-/34' connecting region, can be used to inhibit hexamer assembly at the core region of major contact.
Outer regions of major contact: The sequence variability preceding Argl79(177), influences the number of potential H bonds at the αl-α2 (hexamer) interface. The interactions in the outer region involve the highly conserved loop comiecting the β7 and β8, and β7'-β8' sheets. In the αl-αl major interface of the hexamer, five contiguous carbonyl oxygens of highly conserved Ala74-Asp78 in one chain form hydrogen bonds with side chains Asn77, Argl79, and Tyr 185 of the other chain in symmetrical sets (Fig. 9c). These side chains are also conserved in both αl and α2 chains. However, insertion of Glyl76 and substitution of Asnl74 in α2 sequence alters the orientation conserved Asn78 and Argl77 residues, which results in the few hydrogen bonds in the αl-α2 interface. Therefore, compounds that target the outer regions of major contact at the hexamer interface, such as peptides derived from these regions, can be used to inhibit hexamer assembly. For example, peptides including the sequence ASRND (SEQ TD NO:201) (αl) or YYANA (SEQ ID NO:218) (αl), or the corresponding sequences in the other alpha chains, can be used to inhibit hexamer assembly at the outer region of major contact.
Major-minor junction: The major-minor junction is the area of the hexamer interface where two chains from one trimer contact two chains of the other trimer. There are two types of junctions, one involving three αl and one α2 chains, and the other involving two each of αl and α2 chains. The hydrogen bonding pattern in the two junctions is highly conserved (Figure 7C). Both αl-αl and α2-α2 form a Asnl 87(185)-Tyrl 89(188) (NYY) (SEQ ID NO:297) hydrogen bond pairs in the interface. In addition to this, Asnl 87(185) forms a pair of hydrogen bonds with Arg76(75) of another chain (within the outer region of major contact discussed above) from the opposite trimer. The multiple hydrogen bonds formed by Asnl 87(185) involving residues from two different chains is probably one of the major factors stabilizing the trimer-trimer interface. Therefore, compounds that target major-minor junction at the hexamer interface, such as peptides derived from these regions, can be used to inhibit hexamer assembly. For example, peptides including the sequence NYY (SEQ ID NO:288) (αl) (such as ECHGRGTCNYY (SEQ ID NO: 172)), or corresponding sequences in the other α chains, all of which is present at the hexamer interface (and which includes a large portion of the Intra-CDSR), or ASRND (SEQ TD NO:201) (αl (which includes the ARG76(75) residue), or corresponding sequences in the other α chains, can be used to inhibit hexamer assembly at the major-minor junction. Thus, peptides containing the sequence ASRND (SEQ ID NO:201) can interfere with hexamer assembly by interfering with interactions at both the outer region of major contact and the major-minor junction. Similarly, peptides that target the Intra-CDSR and extend to contain the 2 additional Y residues from the sequence "NYY" (SEQ TD NO:288) can be used to inhibit trimer assembly, as well as hexamer assembly.
Other residues that are located at the hexamer interface, and that are believed to be important for hexamer assembly, include (1) MSMAP (SEQ ID NO: 129) (residues 91-95 αl)/MMP (SEQ ID NO: 132) (α2), and corresponding sequences in the other α chains; (2) PSTLK (SEQ ID NO:177) (residues 208-212 in αl; /39'strand; ADTLK in dl (SEQ ID NO: 180)), and corresponding sequences in the other α chains; (3) FCNINNVCNFA (SEQ TD NO:289) (αl AND o5-co-extensive with the Inter- CDSR), and corresponding sequences in the other α chains: α3: FCNVNDVCNF (SEQ ID NO.298) α2: YCNPGDVCYY (SEQ ID NO:299) α4: YCNIHQVCHY (SEQ ID NO:300) α6: YCNTNEVCHY (SEQ ID NO:301) Thus, peptides containing these sequences, or portions thereof, can be used to inhibit hexamer assembly.
Disulfide bonds: Interchain or Intrachain?
Disulfide cross-linking is a recurring theme in collagen assembly and is believed to play an important role in the stabilization of the trimeric structure (11). Fibrillar procollagens are believed to form interchain disulfide bonds catalyzed by protein disulfide isomerase in either the C-telopeptide or C-propeptide (56, Kiovu, 1987 #343). Interchain disulfides have been proposed to form both in the collagenous and NCI domains of type IV collagen. Whereas the interchain disulfides in the collagenous domains are formed within a protomer to stabilize the collagen triple helix, those in the NCI domains are believed to occur between the protomers to stabilize the network at the C-terminus. Disulfide exchange between NCI domains of similar α chains from two different protomers was proposed as one of the major stabilizing forces in the hexamer assembly (57). Under denaturing conditions, the human placenta derived NCI hexamer dissociated as dimers and monomers. The dimers were shown to be crosslinked predominantly by disulfide bridges. However, a later study by Langeveld et al (55) comparing the NCI hexmers isolated from several BMs revealed rather complex results. Whereas the results of placenta BM and kidney glomerular BM NCI hexamers agreed with the previous observations, dissociating as dimers upon denaturation, the LBM NCI hexamer dissociated predominantly as monomers implying the absence of disulfide cross-linking. The crystal structure of LBM NCI hexamer reveals just that — all the cysteines are involved in intrachain disulfides. Siebold et al (57) proposed disulfide exchanges involving Cys20(20')- Cysll l'(lll) and Cys53(53')-Cysl08'(108) pairs in N-subdomain ( and those in similar positions in C-subdomain) in αl chain resulting in a total of four disulfide crosslinkings in each subdomain based on the cynogen bromide. The topological arrangement of disulfides observed in the crystal structure suggests the possibility for such a rearrangement is extremely remote (Figure 7A). The disulfides in the NCI monomer are arranged in three tiers with Cys20-Cysl ll and Cysl30-Cys225 are close to the triple helical junction, Cys65-Cys71 and Cysl76-Cysl82 are close to the interface and Cys53-Cysl08 and Cysl64-Cys222 lies in between. The disulfide pairs Cys20-Cysll l and Cys53-Cysl08 in the monomers of αlA-αlD dimer are about 70 A and 50 A apart respectively. Thus the possibility for disulfide exchange, if any, exists only for the Cys65-Cys71 and Cysl76-Cysl82 pairs. However, the staggered arrangement of the two trimers brings Cys65-Cys71 pair of αlA closer to its C- subdomain equivalent Cys 176 '-Cys 182' pair of αlD chain rather than its counterpart Cys65'-Cys71' in the N-subdomain. These two closest disulfide pairs in αlA-αlD dimer are about 16 A from each other. Even more importantly, these intrachain disulfides are located in the 3D domain-swapped β-hairpin regions. If the disulfide exchanges were indeed possible between these pairs it would involve major conformational alterations. Such a movement of the β -hairpins containing the "exchangeable" cysteine residues would break both the interchain and intrachain 3D domain swapping interactions, thus destabilizing the trimer structure. From these arguments, it is difficult to envisage disulfide cross-linking between the monomers belonging to two protomers in the present structure. We also examined the possibility of intra-protomer disulfides, which would also require major conformational changes and potentially move the N-terminii of the three chains severely affecting collagen- NCI linkage. An alternative conformation must exist for the NCI domains from all other BMs to account for the inter-protomer disulfide cross-linkings.
Biological Significance. There is very little crystallographic data available on non- collagenous domains. The only available structures of non-coUagenous domains are those of endostatins (58,59), which are homologous fragments of single chains from types XVIII and XV collagens. The present work provides the first unambiguous structural basis for the chain stochiometry of the type IV collagen αl.α2 network, as well as the structural basis for chain specific assembly of type IV collagen. The NCI monomer folds into a novel tertiary structure and the close ended-trimer of (αl)2.α2 is organized through unique 3D domain swapping interactions. These features must be conserved in all type IV collagen networks, from all species, due to overall sequence similarity and very high sequence identity of the regions participating in domain swapping. The chain specificity is determined by the differences in the primary sequences of the hypervariable regions of the NCI domains of the constituent chains, which manifest as different secondary structures at the monomer-monomer interfaces. The hexamer structure is stabilized by the extensive hydrophobic and hydrophilic interactions at the trimer-trimer interface without a need for disulfide cross-linking. The crystal structure of LBM NCI hexamer and the denaturation studies of NCI hexamers from several BMs suggest an alternative conformation must exist in hexamers that are cross-linked by interchain disulfides. Some hitherto unknown enzymatic process might be responsible for folding the same amino acid sequences into different conformations in different tissues.
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62

Claims

1. A polypeptide consisting of at least 8 contiguous amino acids of general formula I:
PF(R1)(R2)CN(R3)(R4)(R5)VC(R6)(R7)A (SEQ ID NO:l)
RI is selected from the group consisting of L, M, A, V, norL, and I; R2 is selected from the group consisting of F and Y; R3 is selected from the group consisting of I, V, L, norL, A, and P; R4 is selected from the group consisting of N, G, and H;
R5 is selected from the group consisting of N, D, Q, and E; R6 is selected from the group consisting of N, Y, and H; and R7 is selected from the group consisting of F and Y.
2. The polypeptide of claim 1 consisting of the amino acid sequence of general formula I.
3. The polypeptide of claim 1 , wherein R2 is F;
R4 is N;
R5 is selected from the group consisting of N and D; R6 is N; and
R7 is F.
4. The polypeptide of claim 1, wherein R2 is Y;
R3 is selected from the group consisting of P and I; R5 is selected from the group consisting of D, Q, and E;
R6 is selected from the group consisting of Y and H; and R7 is Y.
5. The polypeptide of claim 1 wherein the polypeptide is selected from the group consisting of PFLFCNiNNVCNFA (SEQ ID NO:2); PFLFCNVNDVCNFA (SEQ ID NO:3); PFMFCNINNVCNFA (SEQ ID NO:4); PFLYCNPGDVCYYA (SEQ ID NO:5); PFAYCNIHQVCHYA (SEQ ID NO:6); and PFIYCNTNEVCHYA (SEQ ID NO:7).
6. A polypeptide consisting of at least 7 contiguous amino acids of general formula II:
PF(R1)EC(R2)G(R3)(R4)GTC(R5) (SEQ ID NO:8) RI is selected from the group consisting of L, A, V, norL, and I; R2 is selected from the group consisting of H, N, Q, and S;
R3 is selected from the group consisting of G, R, A, or is absent; R4 is selected from the group consisting of R and Q; and R5 is selected from the group consisting of N and H.
7. The polypeptide of claim 6 consisting of the amino acid sequence of general formula II.
8. The polypeptide of claim 6 wherein R2 is H;
R3 is R; R4 is G; and R5 is N.
9. The polypeptide of claims 6 wherein
R2 is selected from the group consisting of N, Q, and S; R3 is selected from the group consisting of G, R, and A; R4 is selected from the group consisting of R and Q; and R5 is H.
10. The polypeptide of claim 6 wherein the polypeptide is selected from the group consisting of PFIECHGRGTCN (SEQ ID NO:9); PFLECHGRGTCN (SEQ ID NO:10); PFIECNGGRGTCH (SEQ ID NO:ll); PFLECQGRQGTCH (SEQ ID NO:12); and PFIECSGARGTCH (SEQ ID NO:13).
11. A polypeptide consisting of at least 13 amino acids selected from the group consisting of:
(a) EFRSAPFIECHGRGTCNYYANA (SEQ ID NO:14),
(b) EFRASPFLECHGRGTCNYYSNS (SEQ ID NO: 15); (c) EFRSAPFIECHGRGTCNYYANS (SEQ ID NO: 16);
(d) DFRATPFIECNGGRGTCHYYA)NK (SEQ ID NO : 17);
(e) DFRAAPFLECQGRQGTCHFFANK (SEQ ID NO: 18); and
(f) DFRATPFIECSGARGTCHYFANK (SEQ ID NO: 19)
12. A chimeric polypeptide consisting of:
(a) a polypeptide according to claim 1;
(b) a polypeptide according to claim 6; and
(c) a polypeptide linker consisting of between 0 and 20 amino acids.
13. The chimeric polypeptide of claim 12 consisting of
(a) a polypeptide according to claim 5;
(b) a polypeptide according to claim 10; and
(c) a polypeptide linker consisting of 2 amino acids. 14. A polypeptide consisting of a sequence of general formula III: F(R1)T(R2) (SEQ ID NO:20) wherein RI is selected from the group consisting of S and T; and R2 is selected from the group consisting of M and L.
15. The polypeptide of claim 14, wherein the polypeptide is selected from the group consisting of FSTM (SEQ ID NO:21), FTTM (SEQ ID NO:22) and FTSL
(SEQ ID NO:23).
16. A polypeptide selected from the group consisting of
(a) X1-FSTM-Z1, wherein XI is 0, 1, 2 ,3, 4, or 5 amino acids of the sequence SCLRK (SEQ ID NO: 24), and Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLFC (SEQ ID NO: 25);
(b) X3-FTTM-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLQR (SEQ ID NO: 27), and Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLFC(SEQ ID NO: 25);
(c) X5-FSTM-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLRR (SEQ ID NO: 29), and Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFMFC (SEQ ID NO: 30);
(d) X2-FSTM-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLAR (SEQ ID NO: 32), and Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFLYC (SEQ ID NO: 33); (e) X4-FSTL-Z4, wherein X4 is 0, 1, 2 ,3, 4, or 5 amino acids of the sequence SCLPV (SEQ ID NO: 35), and Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFAYC (SEQ ID NO: 36); and (f) X6-FSTM-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SCLPR (SEQ ID NO: 38), and Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PFIYC (SEQ ID NO: 39).
17. A polypeptide consisting of a sequence of general formula IV: (R1)MF(R2)K (SEQ ID NO:41) wherein RI is selected from the group consisting of E, R, and D; and R2 is selected from the group consisting of K, R, and S.
18. The polypeptide of claim 17, wherein the polypeptide is selected from the group consisting of EMFKK (SEQ ID NO:42), RMFRK (SEQ ID NO:43), and DMFSK (SEQ ID NO:44).
19. A polypeptide selected from the group consisting of (a) X1-EMFKK-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TIERS (SEQ ID NO: 48), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PTPST (SEQ ID NO: 49);
(b) X3-RMFRK-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLNPE (SEQ ID NO: 51), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PIPST (SEQ ID NO: 52);
(c) X5-DMFSK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVDVS (SEQ ID NO: 54), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PQSET (SEQ ID NO: 55);
20. A polypeptide selected from the group consisting of SFQ (SEQ ID NO:45); LQF (SEQ ID NO:46), and QQF (SEQ ID NO:47).
21. A polypeptide selected from the group consisting of
(a) X2-SFQ-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TIPEQ (SEQ ID NO: 57), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSPSA (SEQ ID NO: 58);
(b) X4-LQF-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVKAD (SEQ ID NO: 60), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SSAPA (SEQ ID NO: 61); and (c) X6-QQF-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TVEER (SEQ ID NO: 63), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GELPV (SEQ ID NO: 64).
22. A polypeptide consisting of a sequence of general formula V: (R1)AH(R2)QD (SEQ ID NO:66) wherein RI is selected from the group consisting of R and K; and R2 is selected from the group consisting of G and N.
23. The polypeptide of claim 22 wherein the polypeptide consists of a sequence selected from the group consisting of RAHGQD (SEQ ID NO:67) and KAHNQD
(SEQ ID NO:68)..
24. A polypeptide selected from the group consisting of
(a) X1-RAHGQD-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNE (SEQ ID NO: 69), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTAG (SEQ ID NO: 70;
(b) X3-RAHGQD-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNQ (SEQ ID NO: 72), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTLG (SEQ ID NO: 73); (c) X5-RAHGQD-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VQGNK (SEQ ID NO: 75), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGTAG (SEQ ID NO: 70);
(d) X2-KAHNQD-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FEGQE (SEQ ID NO: 77), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGLAG (SEQ ID NO: 78);
(e) X4-KAHNQD-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LEGQE (SEQ ID NO: 80), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGLAG (SEQ ID NO: 78); and
(f) X6-KAHNQD-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VEGQE (SEQ ID NO: 82), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LGFAG (SEQ ID NO: 83).
25. A polypeptide consisting of a sequence of general formula VI:
(R1)G(R2)GQ (SEQ ID NO:85) wherein RI is selected from the group consisting of E and Q; and R2 is selected from the group consisting of S, T, and G.
26. The polypeptide of claim 25, wherein the polypeptide is selected from the group consisting of EGSGQ (SEQ ID NO:86), EGTGQ (SEQ ID NO:87), EGGGQ (SEQ ID NO:88) and QGGGQ (SEQ ID NO:89)
27. A polypeptide selected from the group consisting of
(a) X1-EGSGQ-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TSAGA (SEQ ID NO: 90), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALASP (SEQ ID NO: 91);
(b) X3-EGTGQ-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TSAGS (SEQ ID NO: 93), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALASP (SEQ ID NO: 91);
(c) X2-EGGGQ-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAAGD (SEQ ID NO: 95), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLVSP (SEQ ID NO: 96);
(d) X4-QGGGQ-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TGAGD (SEQ ID NO: 98), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ALMSP (SEQ ID NO: 99); and (e) X6-EGGGQ-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAAGA (SEQ ID NO: 101), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLVSP (SEQ ID NO: 96).
28. A polypeptide consisting of a sequence of general formula VII: (R1)G(R2)(R3) (SEQ ID NO:103) wherein RI is selected from the group consisting of Q and E; R2 is selected from the group consisting of N and Q; and R3 is selected from the group consisting of E, Q, and K.
29. The polypeptide of claim 28, wherein RI is Q and R2 is N.
30. The polypeptide of claim 28, wherein the polypeptide is selected from the group consisting of QGNE (SEQ ID NO:104), QGNQ (SEQ ID NO:105), QGNK
(SEQ ID NO:106), and EGQE (SEQ ID NO:107)
31. A polypeptide selected from the group consisting of
(a) X1-QGNE-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYV (SEQ ID NO: 108), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO: 109); (b) X3-QGNQ-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SFLFV (SEQ ID NO: 111), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO: 109);
(c) X5-QGNK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYV (SEQ ID NO:108), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RAHGQ (SEQ ID NO : 109) ;
(d) X2-EGQE-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYF (SEQ ID NO:114), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO:115);
(e) X4-EGQE-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLYL (SEQ ID NO: 117), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO:115); and
(f) X6-EGQE-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SLLFV (SEQ ID NO:119), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KAHNQ (SEQ ID NO:115).
32. The polypeptide of claim 31, wherein the polypeptide is selected from the group consisting of VQGNER (SEQ ID NO: 121), VQGNQR (SEQ ID NO: 122), VQGNKR (SEQ ID NO: 123), FEGQEK (SEQ ID NO: 124), LEGQEK (SEQ ID NO: 125), and VEGQEK (SEQ ID NO: 126).
33. A polypeptide consisting of a sequence of general formula VIII: M(R1)M(R2)P (SEQ ID NO:127) wherein RI is selected from the group consisting of S, N, or is absent; and R2 is selected from the group consisting of A, Q, or is absent. 34. The polypeptide of claim 33 wherein the polypeptide is selected from the group consisting of MSMAP (SEQ ID NO:128), MNMAP (SEQ ID NO:129),
MSMQP (SEQ ID NO:130), and MMP (SEQ ID NO: 131).
35. A polypeptide selected from the group consisting of (a) Xl-MSMAP-Zl, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PEPMP (SEQ ID NO: 132), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ITGEN (SEQ ID NO: 133);
(b) X3-MNMAP-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PALMP (SEQ ID NO: 135), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ITGRA (SEQ ID NO: 136);
(c) X5-MSMQP-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PEPMP (SEQ ID NO:132), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LKGQS (SEQ ID NO: 138); (d) X2-MMP-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAPLP (SEQ ID NO:140), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VAEDE (SEQ ID NO:141);
(e) X4-MMP-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AAPLP (SEQ ID NO:143), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LSEEA (SEQ ID NO : 144); and
(f) X6-MMP-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence TAPIP (SEQ ID NO:146), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VSQTQ (SEQ ID NO:147).
36. A polypeptide selected from the group consisting of PMPMSMAPITG (SEQ ID NO: 149); LMPMNMAPITG (SEQ ID NO:150); PMPMSMQPLKG (SEQ ID NO: 151); PLPMMPVAE (SEQ ID NO: 152); PLPMMPLSE (SEQ ID NO: 153); and PIPMMPVSQ (SEQ ID NO: 154).
37. A polypeptide consisting of a sequence of general formula IX: AG(R1)(R2) (SEQ ID NO:155) wherein RI is selected from the group consisting of A, S and D; and R2 is selected from the group consisting of E and Q.
38. The polypeptide of claim 37 wherein the polypeptide is selected from the group consisting of AGAE (SEQ ID NO:156), AGSE (SEQ ID NO:157), AGDE (SEQ ID NO:158), and AGDQ (SEQ ID NO:159).
39. A polypeptide selected from the group consisting of (a) X1-AGAE-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence VMHTS (SEQ ID NO: 160), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSGQA (SEQ ID NO: 161);
(b) X3-AGSE-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence IMFTS (SEQ ID NO: 163), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GTGQA (SEQ ID NO: 164);
(c) X5-AGAE-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence MMHTS (SEQ ID NO:166), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GSGQA (SEQ ID NO: 161); (d) X2-AGDE-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTA (SEQ ID NO: 168), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQS (SEQ ID NO: 169);
(e) X4-AGDQ-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTG (SEQ ID NO:171), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQA (SEQ ID NO:172); and
(f) X6-AGAE-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence LMHTA (SEQ ID NO:168), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GGGQS (SEQ ID NO:169).
40. A polypeptide consisting of at least 5 contiguous amino acids of general formula X:
EC(R1)G(R2)(R3)GTC(R4)(R5)(R6) (SEQ ID NO:175) wherein RI is selected from the group consisting of H, N, Q, and S;
R2 is selected from the group consisting of G, R, A, or is absent; R3 is selected from the group consisting of R and Q
R4 is selected from the group consisting of N and H;
R5 is selected from the group consisting of F and Y; and
R6 is selected from the group consisting of F and Y.
41. The polypeptide of claim 40, wherein the polypeptide consists of the amino acid sequence of general formula X. 42. The polypeptide of claim 40, wherein
R2 is selected from the group consisting of G, R, A; and
R4 is H.
43. The polypeptide of claims 40 wherein the polypeptide is selected from the group consisting of ECHGRGTCNYY (SEQ ID NO:176), ECNGGRGTCHYY (SEQ ID NO:177), ECQGRQGTCHFF (SEQ ID NO:178), and ECSGARGTCHYF (SEQ ID NO:179).
44. A polypeptide consisting of an amino acid sequence of general formula XI: (R1)(R2)T(R3)K (SEQ ID NO:180) wherein RI is selected from the group consisting of P, S, and A; R2 is selected from the group consisting of S, E, and D; and R3 is selected from the group consisting of L and V.
45. The polypeptide of claim 44 wherein R3 is L.
46. The polypeptide of claim 44 wherein R2 is selected from D and E.
47. The polypeptide of claim 44 wherein the polypeptide is selected from the group consisting of PSTLK (SEQ ID NO:181), PSTVK (SEQ ID NO:182), SETLK
(SEQ ID NO:183), ADTLK (SEQ ID NO:184), and PDTLK (SEQ ID NO:185).
48. A polypeptide selected from the group consisting of
(a) X1-PSTLK-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FKKPT (SEQ ID NO: 186), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGELR (SEQ ID NO: 187);
(b) X3-PSTVK-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FRKPI (SEQ ID NO: 189), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGELE (SEQ ID NO: 190); (c) X5-SETLK-Z5, wherein X5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FSKPQ (SEQ ID NO:192), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGDLR (SEQ ID NO: 193);
(d) X2-ADTLK-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QGSPS (SEQ ID NO:195), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGLIR (SEQ ID NO:196);
(e) X4-PDTLK-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SSAPA (SEQ ID NO:198), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ESQAQ (SEQ ID NO:199); and (f) X6-SETLK-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence GELPV (SEQ ID NO:201), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence AGQLH (SEQ ID NO:202).
49. A polypeptide consisting of an amino acid sequence of general formula XII: A(R1)RND (SEQ ID NO:204) wherein RI is selected from the group consisting of S, Q, and R.
50. The polypeptide of claim 49, wherein the polypeptide sequence is selected from the group consisting of ASRND (SEQ ID NO:205), AQRND (SEQ ID NO:206), and ARRND (SEQ ID NO:207).
51. A polypeptide selected from the group consisting of
(a) Xl-ASRND-Zl, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence NVCNF (SEQ ID NO: 208), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSYWL (SEQ ID NO: 209); (b) X3-ASRND-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence DVCNF (SEQ ID NO: 211), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSYWL (SEQ ID NO: 209);
(c) X2-ASRND-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence DVCYY (SEQ ID NO:213), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KSYWL (SEQ ID NO:214);
(d) X4-AQRND-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QVCHY (SEQ ID NO:216), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RSYWL (SEQ ID NO:217); and
(e) X6-AJ J ND-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence EVCHY (SEQ ID NO:219), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence KSYWL (SEQ ID NO:214).
52. A polypeptide consisting of an amino acid sequence of general formula XIII: (R1)(R2)(R3)N(R4) (SEQ ID NO:221) wherein RI is selected from the group consisting of Y and F;
R2 is selected from the group consisting of Y and F; R3 is selected from the group consisting of A and S; and R4 is selected from the group consisting of A, S, and K.
53. The polypeptide of claim 49, wherein the polypeptide sequence is selected from the group consisting of YYANA (SEQ ID NO:222) YYSNS (SEQ ID NO:223) YYANS (SEQ ID NO:224) YYANK (SEQ ID NO:225) FFANK (SEQ ID NO:226) and YFANK(SEQ ID NO:227).
54. A polypeptide selected from the group consisting of
(a) X1-YYANA-Z1, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229); (b) X3-YYSNS-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229);
(c) X1-YYANS-Z2, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCN (SEQ ID NO: 228), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO: 229);
(d) X2-YYANK-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCH (SEQ ID NO:233), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229);
(e) X4-FFANK-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence QGTCH (SEQ ID NO:235), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229); and
(f) X6-YFANK-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence RGTCH (SEQ ID NO:233), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence YSFWL (SEQ ID NO:229).
55. A polypeptide selected from the group consisting of lERSEMFKKPT (SEQ ID NO:238), LNPERMFRKPI (SEQ ID NO:239), VDVSDMFSKPQ (SEQ ID NO:240), IPEQSFQGSPS (SEQ ID NO:241), VKADLQFSSAPA (SEQ ID NO:242), and VEERQQFGELPV (SEQ ID NO:243).
56. A polypeptide selected from the group consisting of
(a) Xl-IERSEMFKKPT-Zl, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAT (SEQ ID NO: 244), and wherein Zl is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PSTLK (SEQ ID NO: 181); (b) X3-LNPERMFRKPI-Z3, wherein X3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAS (SEQ ID NO: 246), and wherein Z3 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PSTVK (SEQ ID NO: 182);
(c) X1-VDVSDMFSKPQ-Z2, wherein XI is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLAT (SEQ ID NO: 244), and wherein Z5 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SETLK (SEQ ID NO: 183);
(d) X2-IPEQSFQGSPS-Z2, wherein X2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z2 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence ADTLK (SEQ ID NO:184); (e) X4-VKADLQFSSAPA-Z4, wherein X4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z4 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence PDTLK (SEQ ID NO:185); and
(f) X6-VEERQQFGELPV-Z6, wherein X6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence FWLTT (SEQ ID NO:249), and wherein Z6 is 0, 1, 2, 3, 4, or 5 amino acids of the sequence SETLK (SEQ ID NO:183).
57. A polypeptide selected from the group consisting of
FSTMPFLFCNTNNVCNFA (SEQ ID NO: 253), FTTMPFLFCNVNDVCNFA (SEQ ID NO: 254), FSTMPFMFCNiNNVCNFA (SEQ ID NO: 255), FSTMPFLYCNPGDVCYYA (SEQ ID NO: 256), FSTLPFAYCNIHQVCHYA (SEQ ID NO: 257), FSTMPFIYCNINEVCHYA (SEQ ID NO: 258), PFLFCNINNVCNF ASRND (SEQ ID NO: 259), PFLFCNVNDVCNFASRND (SEQ ID NO: 260), PFMFCNiNNVCNFASRND (SEQ ID NO: 261), PFLYCNPGDVCYYASRND (SEQ ID NO: 262), PFAYCNIHQVCHYAQRND (SEQ ID NO: 263), PFIYCNINEVCHYARRND (SEQ ID NO: 264), FSTMPFLFCNINNVCNFASRND (SEQ ID NO: 265), FTTMPFLFCNVNDVCNFASRND (SEQ ID NO: 266), FSTMPFMFCNΓNNVCNFASRND (SEQ ID NO: 267), FSTMPFLYCNPGDVCYYASRND (SEQ ID NO: 268), FSTLPFAYCNTHQVCHYAQRND (SEQ ID NO: 269),
FSTMPFΓYCNΓNEVCHYARRND (SEQ ID NO: 270), PFΓECHGRGTCNΎY (SEQ
ID NO:271), PFLECHGRGTCNYY (SEQ ID NO: 272), PFIECNGGRGTCHYY (SEQ ID NO: 273), PFLECQGRQGTCHFF(SEQ ID NO: 274),
PFIECSGARGTCHYF (SEQ ID NO: 275), JERSEMFKKPTPSTLKAG (SEQ ID NO: 276), LNPERMFRKPff STVKAG (SEQ ID NO:277),
VDVSDMFSKPQSETLKAG (SEQ ID NO: 278), IPEQSFQGSPSADTLKAG (SEQ ID NO: 279), VKADLQFSSAPAPDTLKES (SEQ ID NO: 280), VEERQQFGELPVSETLKAG (SEQ ID NO: 281), GSCLRKFSTM (SEQ ID NO: 282), GSCLQRFTTM (SEQ ID NO:283), GSCLRRFSTM (SEQ ID NO: 284), GSCLARFSTM (SEQ ID NO: 285), GSCLPVFSTL (SEQ ID NO: 286), GSCLPRFSTM (SEQ ID NO: 287), LRKFSTMPFLFCNINNVCNF (SEQ ID NO: 288), LQRFTTMPFLFCNVNDVCNF (SEQ ID NO:289), LRRFSTMPFMFCNΓNNVCNF (SEQ ID NO: 290), LARFSTMPFLYCNPGDVCYY (SEQ ID NO: 291),
LPVFSTLPFAYCNIHQVCHY (SEQ ID NO: 292), LPRFSTMPFIYCNiNEVCHY (SEQ ID NO: 293), IPE (SEQ ID NO:294), IER (SEQ ID NO:295), QD (SEQ ID NO:296), NYY (SEQ ID NO:297), FCNVNDVCNF (SEQ ID NO:298), YCNPGDVCYY (SEQ ID NO:299), YCNIHQVCHY (SEQ ID NO:300), and YCNINEVCHY (SEQ ID NO:301)
58. A pharmaceutical composition comprising:
(a) the polypeptide of any one of claims 1-57; and
(b) a pharmaceutically acceptable carrier.
59. A method for inhibiting angiogenesis in tissue comprising contacting said tissue with an effective inhibiting amount of the polypeptide of any one of claims 1-
57.
60. A method for inhibiting angiogenesis in tissue comprising contacting said tissue with an effective inhibiting amount of the pharmaceutical composition of claim 58.
61. The method of claim 59 or 60 wherein the angiogenesis is tumor-induced.
62. A method for treating an angiogenesis-mediated disease or condition in a mammal, comprising administering to a mammal with an angiogenesis-mediated disease or condition an amount effective to inhibit angiogenesis of the polypeptide of any one of claims 1-57.
63. A method for treating an angiogenesis-mediated disease or condition in a mammal, comprising administering to a mammal with an angiogenesis-mediated disease or condition an amount effective to inhibit angiogenesis of the pharmaceutical composition of claim 58
64. The method of claim 62 or 63 wherein the angiogenesis-mediated disease or condition is selected from the group consisting of solid and blood-borne tumors, diabetic retinopathy, rheumatoid arthritis, retinal neovascularization, choroidal neovascularization, macular degeneration, corneal neovascularization, retinopathy of prematurity, corneal graft rejection, neovascular glaucoma, retrolental fϊbroplasia, epidemic keratoconjunctivitis, Vitamin A deficiency, contact lens overwear, atopic keratitis, superior limbic keratitis, pterygium keratitis sicca, sogrens, acne rosacea, phylectenulosis, syphilis, Mycobacteria infections, lipid degeneration, chemical burns, bacterial ulcers, fungal ulcers, Herpes simplex infections, Herpes zoster infections, protozoan infections, Kaposi's sarcoma, Mooren ulcer, Terrien's marginal degeneration, marginal keratolysis, trauma, systemic lupus, polyarteritis, Wegeners sarcoidosis, scleritis, Steven's Johnson disease, radial keratotomy, sickle cell anemia, sarcoid, pseudoxanthoma elasticum, Pagets disease, vein occlusion, artery occulsion, carotid obstructive disease, chronic uveitis, chronic vitritis, Lyme's disease, Eales disease, Bechets disease, myopia, optic pits, Stargarts disease, pars planitis, chronic retinal detachment, hyperviscosity syndromes, toxoplasmosis, post-laser complications, abnormal proliferation of fibrovascular tissue, hemangiomas, Osler- Weber-Rendu, acquired immune deficiency syndrome, ocular neovascular disease, osteoarthritis, chronic inflammation, Crohn's disease, ulceritive colitis, psoriasis, atherosclerosis, and pemphigoid.
65. A method for inhibiting tumor metastasis, comprising contacting a tumor or tissue with an amount effective to inhibit tumor metastasis of the polypeptide of any one of claims 1-57.
66. A method for inhibiting tumor metastasis, comprising contacting a tumor or tissue with an amount effective to inhibit tumor metastasis of the pharmaceutical composition of claim 58.
67. A method for inhibiting tumor growth, comprising contacting a tumor or tissue with an amount effective to inhibit tumor growth of the polypeptide of any one of claims 1-57.
68. A method for inhibiting tumor growth, comprising contacting a tumor or tissue with an amount effective to inhibit tumor growth of the pharmaceutical composition of claim 58.
69. A method for inhibiting endothelial cell interaction with the extracellular matrix in an animal tissue comprising contacting the tumor or animal tissue with an amount effective to inhibit endothelial cell interaction with the extracellular matrix of the polypeptide of any one of claims 1-57.
70. A method for iώήbiting endothelial cell interaction with the extracellular matrix in an animal tissue comprising contacting the tumor or animal tissue with an amount effective to inhibit endothelial cell interaction with the extracellular matrix of the pharmaceutical composition of claim 58.
71. A method for inhibiting basal lamina membrane formation in cell or tissue development comprising contacting the cell or tissue with an amount effective to inhibit basal lamina membrane formation of the polypeptide of any one of claims 1- 57.
72. A method for inhibiting basal lamina membrane formation in cell or tissue development comprising contacting the cell or tissue with an amount effective to inhibit basal lamina membrane formation of the pharmaceutical composition of claim 58.
73. A crystal of an NCI domain hexamer of type IN collagen, wherein the crystal comprises an [(αl)2.α2]2 ΝC1 hexamer of type IN collagen, wherein the crystal consists of space groups P2\ with approximate a = between 127.16 A and 129.41 A, b = between 139.57A and 143.87 A; c = between 160.20 A and 162.92 A; β = 91.3°, such that the three-dimensional structure of the crystallized ΝC1 domain hexamer can be deteimined to a resolution of 3 A or better.
74. The crystal of claim 73, wherein the three-dimensional structure of the crystallized ΝC1 domain hexamer can be determined to a resolution of 2.2 A or better.
75. The crystal of claim 73, wherein the three-dimensional structure of the crystallized ΝC1 domain hexamer can be determined to a resolution of 2 A or better.
76. A method for identifying inhibitors of type IN collagen assembly, comprising:
(a) obtaining crystals of an ΝC1 hexamer of type IN collagen, wherein the crystal comprises an [(αl)2.α2]2 ΝC1 hexamer of type IN collagen, wherein the crystal consists of space groups P2\ with approximate a = between 127.16 A and 129.41 A, b = between 139.57A and 143.87 A; c = between 160.20 A and 162.92 A; β = 91.3°, such that the three-dimensional structure of the crystallized ΝC1 domain hexamer can be determined to a resolution of 3 A or better.
(b) analyzing the three-dimensional structure of the crystallized ΝC1 domain hexamer of type IV collagen of claim 75; and
(b) designing a potential inhibitor of type IV collagen assembly that targets one or more regions of a type IN collagen ΝC1 α chain selected from the group consisting of:
(i) Intor-chain domain swapping region; (ii) Infra-chain domain swapping region;
(iii) Specificity region;
(iv) Specificity region partner;
(v) Hexamer interface;
(vi) Monomer-monomer interface; and (vii) Hypervariable region.
77. The method of claim 76, further comprising: (a) synthesizing the potential inhibitor; and
(b) determining whether the potential inhibitor inhibits the assembly of type IN collagen.
78 The method of claim 76, further comprising: (a) synthesizing the potential inhibitor; and
(b) conducting an assay to determine whether the potential inhibitor inhibits one or more of angiogenesis, tumor growth, tumor metastasis, endothelial cell adhesion, endothelial cell proliferation, and basal lamina assembly.
79. An inhibitor of type IN collagen assembly identified by the method of any one of claims 76-78.
80. An inhibitor of one or more process selected from the group consisting of angiogenesis, tumor growth, tumor metastasis, endothelial cell adhesion, endothelial cell proliferation, and basal lamina assembly, identified by the method of any one of claims 76-78.
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