Recognition site for the platelet receptor is present on the 15-residue carboxy-terminal fragment of the γ chain of human fibrinogen and is not involved in the fibrin polymerization reaction

Abstract

A pentadecapeptide, derived from a staphylococcal protease digest of the 27-residue carboxy-terminal cyanogen bromide fragment of human fibrinogen γ chain, inhibits binding of 125I-fibrinogen to human platelet receptors and aggregation of platelets induced by ADP and fibrinogen. Amino acid composition and NH 2 terminal analysis indicate that the isolated pentadecapeptide corresponds to residues 397 to 411 of the γ chain. A synthetic peptide also inhibited binding of 125I-fibrinogen and aggregation of platelets. In contrast, the isolated pentadecapeptide and its parent 27-residue fragment lack inhibitory activity toward the polymerization reaction of fibrin monomer. Thus, the site recognizing the platelet receptor encompasses residues 397–411 of the γ chain of fibrinogen and is distinct from the site(s) involved in polymerization of fibrin monomers.