title: Collagen synthesis by human amniotic fluid cells in culture: characterization of a procollagen with three identical proalpha1(I) chains.
abstract: Second trimester human amniotic fluid cells synthesize and secrete a variety of collagenous proteins in culture. F cells (amniotic fluid fibroblasts) are the most active biosynthetically and synthesize predominantly type I with smaller amounts of type III procollagen. Epithelioid AF cells (the predominating clonable cell type) synthesize a type IV-like procollagen and a procollagen with three identical proalpha chains, structurally and immunologically related to the proalpha1 chains of type I procollagen. The latter procollagen, when cleaved with pepsin and denatured, yields a single non-disulfide-bonded alpha chain that migrates more slowly than F cell or human skin alpha1(I) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis but coelutes with these chains from carboxymethyl-cellulose. The major cyanogen bromide produced peptides demonstrate a similar behavior relative to peptides derived from alpha1(I). The collagen is characterized by an increased solubility at neutral pH and high ionic strength, relative to type I collagen. The amino acid composition of the pepsin-resistant alpha chain is essentially identical with that of human alpha1(I), except for marked increases in the content of 3- and 4-hydroxyproline and hydroxylysine. Preliminary experiments suggest that these increased posttranslational modifications are responsible for the unusually slow migration of this collagen and its cyanogen bromide peptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The procollagen has, therefore, been assigned the chain composition [proalpha1(I)]3. Like type I procollagen, [proalpha1(I)]3 undergoes a time-dependent conversion, in the medium and cell layer, to procollagen intermediates and alpha chains. The production of [proalpha1(I)]3 probably reflects the state of differentiation and/or embryologic derivation of AF cells rather than a characteristic of the fetal phenotype, since F cells do not synthesize significant amounts of the procollagen.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000653:Amniotic Fluid / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis* / Q000302:isolation & purification; D005260:Female; D006801:Humans; D003012:Microbial Collagenase; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011347:Procollagen / Q000096:biosynthesis* / Q000302:isolation & purification; D011392:Proline / Q000378:metabolism
chemical_list: D000596:Amino Acids; D010446:Peptide Fragments; D011347:Procollagen; D003094:Collagen; D011392:Proline; D003012:Microbial Collagenase