Fibrinogen Binding to Human Blood Platelets: Effect of ‘y Chain Carboxyterminal Structure and Length

Recent evidence suggests that fibrinogen binding to plate-lets is mediated by the 1 2 carboxyterminal amino acid residues of the ‘y chain. Because human plasma fibrinogen _y chains differ in mol wt and carboxyterminal amino acid sequence. we examined the effect of such y chain hetero-geneity on platelet-fibrinogen interactions. using two fibrinogens of distinct composition. separated by ion exchange chromatography. One fibrinogen possessed only ‘V chains of mol wt 50.000 (F’T#{176}).the predominant ‘y chain species found in plasma. The other fibrinogen possessed equal amounts of ‘y chains with mol wt 50.000 and 57.500 (F’’). with the longer ‘y chain (‘y57.5) possessing an amino acid extension at the carboxyterminal end. The latter fibrinogen was 50 % less effective than F7#{176}in sup-porting ADP-induced platelet aggregation at concentra