Plasma and Platelet Fibrinogen Differ in γ Chain Content

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Abstract
The polypeptide chain composition of fibrinogen and cross- linked fibrin from normal platelets and plasma has been compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fibrinogen was prepared from a lysate of normal human platelets by ethanol precipitation and by antifibrinogen immunoaffinity chromatography. While the Aα chains of platelet fibrinogen appeared to be somewhat degraded, the electrophoretic mobilities of purified platelet and plasma fibrinogen Bβ an γ chains were the same. Crosslinked fibrin was prepared from platelet and plasma fibrinogen and γ chain dimers identified by their electrophoretic mobility, incorporation of the lysine analog dansyl cadaverine during crosslinking, and by reaction with antifibrinogen antibody in Western blots. Platelet crosslinked fibrin had a different polypeptide chain composition than that of plasma crosslinked fibrin with absence of the γ50–γ57.5 dimer in the platelet fibrin. This finding indicates that the γ57.5 chain, which constitutes 5% of total normal plasma fibrinogen γ chains, is either absent or present in markedly reduced amounts in platelet fibrinogen.