title: Heterogeneity of Collagen VI Microfibrils: STRUCTURAL ANALYSIS OF NON-COLLAGENOUS REGIONS.
abstract: Collagen VI, a collagen with uncharacteristically large N- and C-terminal non-collagenous regions, forms a distinct microfibrillar network in most connective tissues. It was long considered to consist of three genetically distinct α chains (α1, α2, and α3). Intracellularly, heterotrimeric molecules associate to form dimers and tetramers, which are then secreted and assembled to microfibrils. The identification of three novel long collagen VI α chains, α4, α5, and α6, led to the question if and how these may substitute for the long α3 chain in collagen VI assembly. Here, we studied structural features of the novel long chains and analyzed the assembly of these into tetramers and microfibrils. N- and C-terminal globular regions of collagen VI were recombinantly expressed and studied by small angle x-ray scattering (SAXS). Ab initio models of the N-terminal globular regions of the α4, α5, and α6 chains showed a C-shaped structure similar to that found for the α3 chain. Single particle EM nanostructure of the N-terminal globular region of the α4 chain confirmed the C-shaped structure revealed by SAXS. Immuno-EM of collagen VI extracted from tissue revealed that like the α3 chain the novel long chains assemble to homotetramers that are incorporated into mixed microfibrils. Moreover, SAXS models of the C-terminal globular regions of the α1, α2, α4, and α6 chains were generated. Interestingly, the α1, α2, and α4 C-terminal globular regions dimerize. These self-interactions may play a role in tetramer formation.
authors.affiliation: From the Center for Biochemistry, Medical Faculty.
authors.forename: Tobias
authors.initials: T
authors.lastname: Maaß
authors.affiliation: the Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, United Kingdom.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Bayley
authors.affiliation: the Department of Clinical Sciences, Division of Infection Medicine, Lund University, SE-221 84 Lund, Sweden, and.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.affiliation: From the Center for Biochemistry, Medical Faculty.
authors.forename: Sandra
authors.initials: S
authors.lastname: Lettmann
authors.affiliation: the Department of Molecular Medicine, University of Padova, 35131 Padova, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bonaldo
authors.affiliation: From the Center for Biochemistry, Medical Faculty, Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases, and Center for Musculoskeletal Biomechanics, University of Cologne, D-50931 Cologne, Germany.
authors.forename: Mats
authors.initials: M
authors.lastname: Paulsson
authors.affiliation: the Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, United Kingdom, clair.baldock@manchester.ac.uk.
authors.forename: Clair
authors.initials: C
authors.lastname: Baldock
authors.affiliation: From the Center for Biochemistry, Medical Faculty, Center for Molecular Medicine, raimund.wagener@uni-koeln.de.
authors.forename: Raimund
authors.initials: R
authors.lastname: Wagener
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D024141:Collagen Type IV / Q000737:chemistry*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D017510:Protein Folding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary
chemical_list: D024141:Collagen Type IV
keywords: VWA domain; collagen; electron microscopy (EM); extracellular matrix; microfibrils; single particle analysis; small-angle x-ray scattering (SAXS)