title: Proteolytic cleavage of vitamin K-dependent bovine plasma protein S by alpha-thrombin and plasma serine protease.
abstract: It is known that protein S, a vitamin K-dependent plasma protein, isolated from a human source, gives a closely spaced doublet on sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction and that this heterogeneity in molecular size results from a limited proteolysis of protein S mediated by alpha-thrombin in human species. We found here that alpha-thrombin also rapidly converted single-chain bovine protein S to a nicked form, which consisted of the NH2-terminal segment containing gamma-carboxyglutamic acid and the COOH-terminal large segment bridged by a disulfide linkage(s). These two segments were isolated and chemically characterized after S-alkylation of the nicked protein S. The results suggest that the alpha-thrombin-catalyzed hydrolysis of protein S probably occurs at a peptide linkage (Arg-Ser) located in the NH2-terminal portion. The conversion of single-chain protein S to the nicked form was also mediated by plasma kallikrein and plasmin, in addition to alpha-chymotrypsin and trypsin. However, the alpha-thrombin-catalyzed conversion did not occur when calcium ions were added to the reaction mixture.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000097:blood / Q000494:pharmacology*; D006023:Glycoproteins / Q000097:blood*; D006868:Hydrolysis; D066298:In Vitro Techniques; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D011487:Protein Conformation / Q000187:drug effects; D017293:Protein S; D012697:Serine Endopeptidases; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology*; D014812:Vitamin K / Q000494:pharmacology
chemical_list: D006023:Glycoproteins; D010446:Peptide Fragments; D017293:Protein S; D014812:Vitamin K; D010450:Endopeptidases; D012697:Serine Endopeptidases; D013917:Thrombin; D002118:Calcium