DISSECTING CLOT RETRACTION AND PLATELET-AGGREGATION - CLOT RETRACTIONDOES NOT REQUIRE AN INTACT FIBRINOGEN GAMMA-CHAIN C-TERMINUS

Fibrinogen mediates the processes of platelet aggregation and clot ret raction. Previous studies have demonstrated that fibrinogen binding to the platelet receptor alpha(IIb)beta(3) requires the C-terminal resid ues of the fibrinogen gamma chain. We made a recombinant human fibrino gen that lacks the gamma chain C-terminal four residues (AGDV). As exp ected this fibrinogen did not support platelet aggregation. Unexpected ly, this variant did support clot retraction that was indistinguishabl e from re traction with normal recombinant or plasma fibrinogen. These results suggest that the site on fibrinogen that is required for plat elet aggregation differs from the site on fibrin that is required for clot retraction.