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Interaction of S-protein of complement with thrombin and antithrombin III during coagulation. Protection of thrombin by S-protein from antithrombin III inactivation.

1986; Elsevier BV; Volume: 261; Issue: 16 Linguagem: Inglês

10.1016/s0021-9258(17)38403-x

1083-351X

Eckhard R. Podack, Björn Dahlbäck, John H. Griffin,

Coagulation, Bradykinin, Polyphosphates, and Angioedema

S-protein, the inhibitor in plasma of the membrane attack complex of complement, appears to have a second function in coagulation.S-protein during clotting enters into a trimolecular complex with thrombin and antithrombin I11 (ATIII).Functionally, S-protein in the presence of low concentrations of heparin, protects thrombin from inactivation by ATIII.Complex formation between S-protein and thrombin, and between S-protein, thrombin, and ATIII, was demonstrated by agarose gel electrophoresis and by twodimensional immunoelectrophoresis of purified proteins and in recalcified, clotted plasma.Formation of the trimolecular S-thrombin-AT111 complex was strictly dependent on the presence of thrombin.No association was detectable between S-protein and ATIII or between S-protein and prothrombin.Heparin was not required for the formation of the bimolecular S-protein-thrombin complex or the trimolecular S-protein-ATIII complex.The protective effect of S-protein on inactivation of thrombin by ATIU was demonstrated in functional assays with purified proteins and in plasma only in the presence of low concentrations of heparin.Thus, S - protein may mediate its effect by scavenging heparin required for ATIII activation.It is suggested that the protection of thrombin by S-protein from inactivation by ATIII may be of physiological importance.