Inhibition of platelet aggregation by the recombinant cysteine-rich domain of the hemorrhagic snake venom metalloproteinase, atrolysin A.

The P-III class of venom metalloproteinases has, in addition to the proteinase domain, a disintegrin-like domain and a cysteine-rich domain. Recent evidence has shown that the nonproteinase domains of the P-III class of hemorrhagic metalloproteinases function in the inhibition of platelet aggregation by blocking essential procoagulant integrins on platelets. A specific role for the highly conserved cysteine-rich domain has yet to be described. In this study, we expressed the cysteine-rich domain from the hemorrhagic metalloproteinase atrolysin A and demonstrated its ability to inhibit collagen-stimulated platelet aggregation. Additionally, the cysteine-rich domain was shown to interact with MG-63 cells to inhibit adhesion to collagen I. These data suggest a functional role for the cysteine-rich domain of the P-III toxins in the observed coagulopathy by targeting the toxin to platelets and inhibiting collagen-stimulated platelet aggregation. These characteristics may function to synergistically increase the hemorrhagic effect of the toxins.