title: The supramolecular organization of collagen VI microfibrils.
abstract: Collagen VI has a ubiquitous distribution throughout connective tissues, and has key roles in linking cells and matrix macromolecules. We have generated three-dimensional reconstructions of collagen VI microfibrils using automated electron tomography (AET) in order to obtain new insights into the organisation of collagen VI in assembled microfibrils. Analysis of the reconstruction data has allowed the resolution of the double-beaded structure into smaller subunits. Volume calculations from the tomography data indicate that ten and six A-domains could be packed into the N and C-terminal regions from each monomer, respectively. A putative location for the globular N-terminal regions of the alpha3 chain, important for microfibril assembly and function, has been identified. Some surfaces of the alpha3 chain N-terminal domains appear to be exposed on the surface of a microfibril, where they may provide an interactive surface for molecules. Analysis of the interbead region provides evidence for complex triple helical supercoiling in microfibrils. Frequently, two strands were visualised emerging from the beaded region and merging into a single interbead region. Measurements taken from the AET data show that there is a decrease in periodicity from dimer/tetramer to microfibrils. Molecular combing reverses this effect by mechanically increasing periodicity to give measurements similar to the component dimers/tetramers. Together, these data have provided important new insights into the organisation and function of these large macromolecular assemblies.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, 2.205 Stopford Building, M13 9PT, Manchester, UK. clair.baldock@man.ac.uk
authors.forename: Clair
authors.initials: C
authors.lastname: Baldock
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sherratt
authors.forename: C Adrian
authors.initials: CA
authors.lastname: Shuttleworth
authors.forename: Cay M
authors.initials: CM
authors.lastname: Kielty
mesh_terms: D000818:Animals; D002417:Cattle; D024142:Collagen Type VI / Q000737:chemistry* / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D018625:Microscopy, Atomic Force; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D014054:Tomography / Q000379:methods
chemical_list: D024142:Collagen Type VI; D046911:Macromolecular Substances; D021122:Protein Subunits