Collagen: Difference between revisions

'''Collagen''', the most abundant protein in vertebrates, is an extracellular, inextensible fibrous protein that comprises the major protein component of such stress-bearing structures as bones, tendons, and ligaments.  As with all fibrous proteins collagen is, for the most part, characterized by highly repetitive simple sequence. Here we study two model compounds (The structure of [[4clg]]<ref>J.M. Chen, C.E. Kung, S.H. Feairheller, E.M. Brown, AN ENERGETIC EVALUATION OF A "SMITH" COLLAGEN MICROFIBRIL MODEL, <I>J. Protein Chem., </I>'''10''', 535, 1991</ref> is shown in the applet to the right.) for naturally occurring collagen, in order to develop an understanding of the fibrous portion of collagen and to show how the different levels of protein structure come together and form a highly ordered and stable fiber.  Collagen's properties of rigidity and inextensibility are due to this highly ordered structure. The part of collagen without structural order is not illustrated in this model. This part of the protein complex having a different amino acid composition, lysine and hydroxylysine are particularly important residues, is globular in nature and not as structurally organized. Lysine and hydroxylysine form covalent crosslinks in the protein complex, thereby adding strength and some flexibility to the fiber. This covalent crosslinking continues throughout life and produces a more rigid collagen and brittle bones in older adults. Go to [[Collagen Structure & Function]] for information on the functions and disorders of collagen and a link in the External Links section of this page for assembly movies of the triple helix of types I and IV.