title: Supramolecular organization of the α121-α565 collagen IV network.
abstract: Collagen IV is a family of 6 chains (α1-α6), that form triple-helical protomers that assemble into supramolecular networks. Two distinct networks with chain compositions of α121 and α345 have been established. These oligomerize into separate α121 and α345 networks by a homotypic interaction through their trimeric noncollagenous (NC1) domains, forming α121 and α345 NC1 hexamers, respectively. These are stabilized by novel sulfilimine (-S=N-) cross-links, a covalent cross-link that forms between Met(93) and Hyl(211) at the trimer-trimer interface. A third network with a composition of α1256 has been proposed, but its supramolecular organization has not been established. In this study we investigated the supramolecular organization of this network by determining the chain identity of sulfilimine-cross-linked NC1 domains derived from the α1256 NC1 hexamer. High resolution mass spectrometry analyses of peptides revealed that sulfilimine bonds specifically cross-link α1 to α5 and α2 to α6 NC1 domains, thus providing the spatial orientation between interacting α121 and α565 trimers. Using this information, we constructed a three-dimensional homology model in which the α565 trimer shows a good chemical and structural complementarity to the α121 trimer. Our studies provide the first chemical evidence for an α565 protomer and its heterotypic interaction with the α121 protomer. Moreover, our findings, in conjunction with our previous studies, establish that the six collagen IV chains are organized into three canonical protomers α121, α345, and α565 forming three distinct networks: α121, α345, and α121-α565, each of which is stabilized by sulfilimine bonds between their C-terminal NC1 domains.
authors.affiliation: From the Division of Nephrology and Hypertension, Department of Medicine.
authors.forename: Wesley E
authors.initials: WE
authors.lastname: Robertson
authors.affiliation: Department of Biochemistry, Proteomics Laboratory-Mass Spectrometry Research Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
authors.forename: Kristie L
authors.initials: KL
authors.lastname: Rose
authors.affiliation: From the Division of Nephrology and Hypertension, Department of Medicine, Department of Biochemistry, Center for Matrix Biology, Department of Pathology, Microbiology, and Immunology, and.
authors.forename: Billy G
authors.initials: BG
authors.lastname: Hudson
authors.affiliation: From the Division of Nephrology and Hypertension, Department of Medicine, Center for Matrix Biology, roberto.vanacore@vanderbilt.edu.
authors.forename: Roberto M
authors.initials: RM
authors.lastname: Vanacore
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta / Q000737:chemistry; D001485:Basement Membrane; D002417:Cattle; D024141:Collagen Type IV / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D008239:Lysine / Q000737:chemistry; D013058:Mass Spectrometry; D008715:Methionine / Q000737:chemistry; D011487:Protein Conformation; D060066:Protein Interaction Maps; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry*
chemical_list: D024141:Collagen Type IV; D021122:Protein Subunits; D008715:Methionine; D008239:Lysine
keywords: Basement Membrane; Collagen; Extracellular Matrix; Extracellular Matrix Protein; Hydroxylysine (Hyl); Mass Spectrometry (MS); Protein Cross-linking; Smooth Muscle; Sulfilimine Bond; Vascular Smooth Muscle Cells