Affinity labeling of a human platelet membrane protein with 5'-p-fluorosulfonylbenzoyl adenosine. Concomitant inhibition of ADP-induced platelet aggregation and fibrinogen receptor exposure.

摘要: Abstract Incubation of washed human blood platelets with 5'-p-fluorosulfonylbenzoyl [3H]adenosine (FSBA) covalently labels a single polypeptide Mr = 100,000. Protection by ADP has suggested that an receptor on the platelet surface membrane was modified. The modified cells, unlike native platelets, failed to aggregate in response (100 microM) and fibrinogen (1 mg/ml). extent binding 125I-fibrinogen aggregation inhibited degree related incorporation 5'-p-sulfonylbenzoyl adenosine (SBA) into indicating FSBA could inhibit exposure receptors necessary for aggregation. SBA alpha-chymotrypsin cleaved labeled concomitantly reversed inhibition binding. Platelets proteolytically digested chymotrypsin prior did not require Moreover, subsequent or affinity reagent can displace bound presence ADP, as well promote rapid disaggregation platelets. apparent initial pseudo-first order rate constant dissociation linearly proportional concentrations. These studies suggest be altered either ADP-induced conformational changes proteolysis reveal latent after