title: Intermediates in the limited proteolytic conversion of procollagen to collagen.
abstract: The conversion of chick bone procollagen to collagen proceeds in a stepwise fashion to produce a limited number of intermediates. Initial proteolytic cleavages remove NH2-terminal nonhelical extensions and yield an intermediate which remains disulfide-bonded via COOH-terminal extensions. Subsequent stepwise scission of one or two chains of the triple-stranded molecule in its COOH-terminal domain produces intermediates which can only be distinguished after dissociation of the noncovalently bonded alpha chains. A final cleavage in this region produces the collagen molecule and a disulfide-bonded triple-stranded fragment which represents the COOH-terminal domain. In all likelihood the endopeptidases which effect cleavage in the NH2- and COOH-terminal regions differ. More than two enzymes may be required for conversion of procollagen to collagen if the nonhelical domains are not released in an en bloc fashion.
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D002642:Chick Embryo; D003094:Collagen / Q000096:biosynthesis* / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D009924:Organ Culture Techniques; D011498:Protein Precursors / Q000276:immunology / Q000378:metabolism*; D011863:Radioimmunoassay
chemical_list: D011498:Protein Precursors; D003094:Collagen