Evidence for a thiol ester in duck ovostatin (ovomacroglobulin).

摘要: The structure and the mechanism for proteinase inhibition of egg white protein ovostatin (ovomacroglobulin) are similar to those plasma alpha 2-macroglobulin, but previous studies have shown that chicken lacks a reactive thiol ester (Nagase, H., Harris, E. D., Jr. (1983) J. Biol. Chem. 258, 7490-7498). Here we show duck has conserved such is capable inhibiting both metallo- serine proteinases stoichiometrically. Evidence esters was established by following results with ovostatin: 1) autolysis into fragments Mr = 123,000 60,000 occurred heating in sodium dodecyl sulfate, prevented treatment CH3NH2; 2) covalent linkages were formed on complex formation; 3) reaction CH3NH2 generated 3.6 SH groups/mol, 3.9 mol [14C]CH3NH2 incorporated per protein; 4) saturation liberated 3.8 groups/mol inhibitor. Conformational rearrangement upon reacting or demonstrated an increased mobility polyacrylamide gel electrophoresis. CH3NH2-treated able bind inhibit without forming bonds, but, unlike unmodified ovostatin, its inhibitory activity destroyed freezing thawing. Complexes between not dissociable except under denaturing conditions. These other evidence indicate bond formation through separate process from trapping this family proteins.