Synthetic RGD peptides derived from the adhesive domains of snake-venom proteins: evaluation as inhibitors of platelet aggregation.

Synthetic peptides based on the RGD domains of the potent platelet aggregation inhibitors kistrin and dendroaspin were generated. The 13-amino-acid peptides were synthesized as dicysteinyl linear and disulphide cyclic forms. In platelet-aggregation studies, the cyclic peptides showed 3-fold better inhibition than their linear equivalents and approx. 100-fold greater potency than synthetic linear RGDS peptides derived from fibronectin. An amino acid substitution, Asp10-->Ala, in the kistrin-based peptide gave a 4-fold decrease in potency in the linear peptide, but produced a 2-fold elevation in the inhibitory activity of the cyclic form, generating a peptide of potency comparable with that of the parent protein.