title: Catalytically competent human and bovine zeta-thrombin and chimeras generated from unfolded polypeptide chains.
abstract: Human and bovine alpha-thrombin cleaved at the B-chain by chymotrypsin generates catalytically competent zeta-thrombins, which are comprised of two noncovalently linked fragments: a 36-(human) or 49-(bovine) residue A-chain linked by a disulfide to B-chain residues B1-148 (zeta 1-thrombin) and B-chain residues B149-259 (zeta 2-thrombin). Human and bovine D-Phe-Pro-Arg-CH2-zeta- and PhMeSO2-zeta-thrombins were prepared by reaction of the active-site histidine (H-B43) and serine (S-B205) with PPACK and PMSF, respectively. Unfolding and dissociation of the noncovalently linked polypeptide chains of either human or bovine D-Phe-Pro-Arg-CH2-zeta- and PhMeSO2-zeta-thrombins in 4.5 M guanidine-HCl and refolding upon 30-fold dilution in 50 mM sodium phosphate buffer pH 6.5, 750 mM NaCl, 0.1% PEG resulted in biphasic generation of catalytic activity. The slow phase was eliminated in the presence of the competitive inhibitor benzamidine-HCl. Unfolding and refolding mixtures of the appropriate inactive precursors generated the active chimeric thrombins bovine zeta 1-thrombin:human zeta 2-thrombin and human zeta 1-thrombin:bovine zeta 2-thrombin. Human zeta 1-thrombin and zeta 2-thrombin were isolated, and, upon recombining, the isolated fragments refolded to generate catalytically competent zeta-thrombin with an active-site content, specific activity toward Chromozym-TH, and a specificity constant (kcat/Km) for FPA release from fibrinogen that were all within 60% of those of native alpha-thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Biological Chemistry Department, Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486.
authors.forename: S D
authors.initials: SD
authors.lastname: Lewis
authors.forename: D V
authors.initials: DV
authors.lastname: Brezniak
authors.forename: J W
authors.initials: JW
authors.lastname: Fenton
authors.forename: J A
authors.initials: JA
authors.lastname: Shafer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013917:Thrombin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D006146:Guanidines; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D002918:Chymotrypsin; D013917:Thrombin; D019791:Guanidine