Blood coagulation inhibitor (disintegrin) superfamily

Disintegrins are a family of small proteins from viper venoms that function as potent inhibitors of both platelet aggregation and integrin-dependent cell adhesion [15578957, 15974889]. Integrin receptors are 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 (Arg-Gly-Asp) or KGD (Lys-Gly-Asp) 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 [12050803]. The role of disintegrin in preventing blood coagulation renders it of medical interest, particularly with regard to its use as an anti-coagulant [16918409].

Disintegrins from different snake species have been characterised: albolabrin, applagin, barbourin, batroxostatin, bitistatin, obtustatin [12742023], schistatin [16101289], echistatin [15535803], elegantin, eristicophin, flavoridin [14499613], halysin, kistrin, tergeminin, salmosin [14661951] and triflavin.

Disintegrin-like proteins are found in various species ranging from slime mold to humans. Some other proteins known to contain a disintegrin domain are:

• Some snake venom zinc metalloproteinases [15962120] consist of an N-terminal catalytic domain fused to a disintegrin domain. Such is the case for trimerelysin I (HR1B), atrolysin-e (Ht-e) and trigramin. It has been suggested that these proteinases are able to cleave themselves from the disintegrin domains and that the latter may arise from such a post-translational processing.
• The beta-subunit of guinea pig sperm surface protein PH30 [1552944]. PH30 is a protein involved in sperm-egg fusion. The beta subunit contains a disintegrin at the N-terminal extremity.
• Mammalian epididymial apical protein 1 (EAP I) [1417724]. EAP I is associated with the sperm membrane and may play a role in sperm maturation. Structurally, EAP I consists of an N-terminal domain, followed by a zinc metalloproteinase domain, a disintegrin domain, and a large C-terminal domain that contains a transmembrane region.