Echistatin

Glu-Cys-Glu-Ser-Gly-Pro-Cys-Cys-Arg-Asn-Cys-Lys-Phe-Leu-Lys-Glu-Gly-Thr-Ile-Cys-Lys-Arg-Ala-Arg-Gly-Asp-Asp-Met-Asp-Asp-Tyr-Cys-Asn-Gly-Lys-Thr-Cys-Asp-Cys-Pro-Arg-Asn-Pro-His-Lys-Gly-Pro-Ala-Thr

Echistatin is a single chain 49 amino acid residue protein, which prevents the aggregation of platelets. It has an isoelectric point (pI) of 8.3 and a molecular weight of 5400. This peptide is present in the venom of Echis carinatus, which is a saw-scaled viper. It contains the arginine-glycine-aspartic (RGD) acid sequence, which is present in proteins that bind to glycoprotein IIb/IIIa complex. It shares the proline-arginine-asparagine-proline sequence with the Aα chain of human fibrinogen. This protein is a member of disintegrin family, which prevents cell adhesion. With regards to molecular weight, echistatins are the smallest member of disintegrin family, and contains four isoforms called, α1, α2, β and γ.

Echistatin has been used:

• as an inhibitor of integrin function to study the role of microfibril-associated glycoprotein-1 (Magp1) in the morphogenesis of vascular structures
• for the preparation of microbubbles targeted to αvβ3 integrins in tumor angiogenesis imaging
• as a conjugate to αvβ3 in flow cytometric binding studies

A member of the disintegrins family, a novel family of integrin β1 and β3 inhibitor proteins and the most potent known inhibitors of integrin function.

Disintegrins represent a novel family of integrin β1 and β3 inhibitor proteins isolated from viper venoms. They are low molecular-weight, cysteine-rich peptides containing the Arg-Gly-Asp (RGD) sequence. They are the most potent known inhibitors of integrin function. Disintegrins interfere with cell adhesion to the extracellular matrix, including adhesion of melanoma cells and fibroblasts to fibronectin, and are potent inhibitors of platelet aggregation.

Echistatin is a disintegrin, which prevents the aggregation of platelets. They interact with and prevent the binding of fibrinogen to their receptors on the membrane of platelets. It also inhibits platelet aggregation mediated by epinephrine, thrombin, collagen, or platelet-activating factor. Studies in isolated osteoclasts show that this peptide inhibits bone resorption by osteoclasts, most probably by damaging adhesion structures.