Disintegrin


Disintegrins are a family of small proteins from viper venoms that function as potent inhibitors of both platelet aggregation and integrin-dependent cell adhesion.

Operation

Disintegrins work by countering the blood clotting steps, inhibiting the clumping of platelets. They interact with the beta-1 and -3 families of integrins receptors. Integrins are cell receptors involved in cell–cell and cell–extracellular matrix interactions, serving as the final common pathway leading to aggregation via formation of platelet–platelet bridges, which are essential in thrombosis and haemostasis. Disintegrins contain an RGD or KGD sequence motif that binds specifically to integrin IIb-IIIa receptors on the platelet surface, thereby blocking the binding of fibrinogen to the receptor–glycoprotein complex of activated platelets. Disintegrins act as receptor antagonists, inhibiting aggregation induced by ADP, thrombin, platelet-activating factor and collagen. The role of disintegrin in preventing blood coagulation renders it of medical interest, particularly with regard to its use as an anti-coagulant.

Types of disintegrin

Disintegrins from different snake species have been characterised: albolabrin, applagin, barbourin, batroxostatin, bitistatin, obtustatin, schistatin, echistatin, elegantin, eristicophin, flavoridin, halysin, kistrin, mojastin, rubistatin, tergeminin, salmosin, tzabcanin and triflavin.
Disintegrins are split into 5 classes: small, medium, large, dimeric, and snake venom metalloproteinases.
Small Disintegrins: 49-51 amino acids, 4 disulfide bonds
Medium Disintegrins: 70 amino acids, 6 disulfide bonds
Large Disintegrins: 84 amino acids, 7 disulfide bonds
Dimeric Disintegrins: 67 amino acids, 4 intra-chain disulfide bonds
Snake Venom Metalloproteinases: 100 amino acids, 8 disulfide bond

Evolution of disintegrin family

Disintegrins evolved via gene duplication of an ancestral protein family, the ADAM family. Small, medium, large, and dimeric disintegrin family are found only in the family Viperidae, suggesting duplication and diversification about 12-20 million years ago. Snake venom metalloproteinases are found through the entire superfamily Colubroidea, suggesting that they evolved before Colubroidea diversified roughly 60 million years ago.