title: Evidence for procollagen, a biosynthetic precursors of collagen.
abstract: Incubation of rat calvaria for short times in the presence of a labeled amino acid revealed the existence of a collagen fraction (procollagen) that functions as a biosynthetic precursor of collagen. Procollagen contains an alpha1-like chain (pre-alpha1) that elutes earlier from CM-cellulose than does rat-bone alpha1 and has a molecular weight, estimated by acrylamide gel electrophoresis, of 120,000. A time-dependent conversion of pre-alpha1 to alpha1 was demonstrated by incubation of calvaria for periods varying from 9 to 60 min and by a pulse-chase experiment. Limited cleavage of procollagen with pepsin resulted in a molecule with a chain resembling alpha1 in chromatographic properties, molecular weight, and relative hydroxyproline and proline contents. Thus, conversion of procollagen to collagen is likely to occur in vivo by a proteolytic mechanism. The additional peptide sequences in procollagen may serve to initiate chain association in triple-helix formation, to facilitate molecular transport, and to inhibit intracellular fibrogenesis.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002247:Carbon Isotopes; D002498:Centrifugation; D002845:Chromatography; D003094:Collagen / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D046508:Culture Techniques; D004589:Electrophoresis, Disc; D005624:Frontal Bone / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D006909:Hydroxyproline / Q000032:analysis; D008970:Molecular Weight; D010294:Parietal Bone / Q000378:metabolism; D010434:Pepsin A / Q000494:pharmacology; D011392:Proline / Q000032:analysis / Q000378:metabolism; D051381:Rats; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D014316:Tritium; D003094:Collagen; D011392:Proline; D010434:Pepsin A; D006909:Hydroxyproline; D005998:Glycine