General Description
Collagen alpha-3(VI) chain (UniProt P12111; also known as Collagen VI alpha-3 polypeptide) is encoded by the COL6A3 gene (Gene ID 1293) in human. Type VI collagen is an extracellular matrix (ECM) component present in virtually all connective tissues, including cartilage, bone, tendon, muscles and cornea, where it forms microfibrils in close association with basement membranes. In addition to anchoring the basement membrane to the pericellular matrix in muscle, research also indicates a role for collagen VI in cell signaling and cell migration. The basic structural unit of collagen VI is a heterotrimer composed of the alpha-1(VI), alpha-2(VI), and alpha-3(VI) chains (encoded by the COL6A1, COL6A2, and COL6A3 genes, respectively). The α1(VI) and α2(VI) chains are similar in size and domain structure, they contain a 335- or 336-amino acid triple helix region that is characteristic of all collagens. Flanking the triple helix are domains homologous to the A-type domains found in von Willebrand factor (VWA domains). α1(VI) and α2(VI) contain one VWA domain N-terminal to the triple helix (N1) and two VWA domains C-terminal of the helix (C1 and C2). The α3(VI) chain, on the other hand, is much larger with 10 N-terminal (N1–N10) and two C-terminal VWA domains (C1 and C2), and several other types of identifiable domains in the C terminal region (C3–C5). Mutations in the COL6A1, COL6A2, and COL6A3 genes are known causes of Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM). Three additional type VI collagen chains have been reported in 2008 (α4(VI), α5(VI) and α6(VI) chains encoded by COL6A4, COL6A5, and COL6A6, respectively).
