Isolation and Properties of a Thrombin-sensitive Protein from Human Blood Platelets

Abstract

A thrombin-sensitive protein has been isolated from human blood platelets by gel electrophoresis followed by filtration through Sephadex.The isolated protein was homogeneous on disc gel and behaved like a P-globulin.In immunoelectrophoresis, a single precipitin line was observed with antiplatelet serum or anti-fibrin-stabilizing factor serum.The precipitin line as well as the protein band on disc gel could not be detected when the protein was treated with thrombin.This protein, denoted platelet fibrin-stabilizing factor, has factor XIII activity which became more and more stable with further purification.Immunodifksion studies showed platelet fibrin-stabilizing factor to be only partially identical with plasma fibrin-stabilizing factor.The molecular weight of platelet fibrin-stabilizing factor as determined by gel IYtration through previously calibrated columns of Sephadex was between 110,000 and 150,000 compared to a value of 160,000 to 350,000 for plasma fibrin-stabilizing factor.It has been concluded that platelet fibrin-stabilizing factor is a smaller and di#erent molecule from plasma fibrin-stabilizing factor.