Characterization of a monomeric disintegrin, ocellatusin, present in the venom of the Nigerian carpet viper, Echis ocellatus.

Ocellatusin is a new RGD-containing short monomeric disintegrin. It is a better inhibitor of alpha(5)beta(1) integrin and a more potent inducer of the expression of a ligand-induced binding site epitope on beta(1) integrin subunit than echistatin. In further contrast to echistatin, ocellatusin has a direct chemotactic stimulus on human neutrophils in vitro. The distinct effects of these two close evolutionarily related disintegrins might be explained by the presence of methionine-22 and histidine-29 in the RGD loop of ocellatusin, which are arginine and aspartic acid, respectively, in echistatin. These mutations may modulate the conformation and/or recognition properties of the integrin-binding loop of ocellatusin.