Triflavin, an RGD-containing antiplatelet peptide, binds to GPIIIa of ADP-stimulated platelets

Triflavin, an Arg-Gly-Asp-containing snake venom peptide, inhibits platelet aggregation through the blockade of fibrinogen binding to the activated platelets. It binds to fibrinogen receptors associated with the glycoprotein IIb/IIIa complex with a Kd value of 7×10^-8 M. In this report, a chemical cross-linking approach was used to further characterize the binding components of triflavin on platelet membrane. ¹²⁵I-triflavin binding was performed with the aid of a chemical cross-linking reagent, DTSSP. Analysis of the cross-linked products by SDS-PAGE (7.5% gel) and subsequent autoradiogram revealed that ¹²⁵I-triflavin was cross-linked specifically to a protein with an apparent molecular weight of 1.1×10⁵, and this reaction was inhibited by GRDGS and excess of non-labeled triflavin. This 110 KDa component was identified to be GpIIIa, recognized by AP₃, a mAb against GpIIIa, by immunoblotting technique. These results indicate that the triflavin-binding sites on platelets reside at a site in close proximity to GpIIIa.