Metalloproteases Affecting Blood Coagulation, Fibrinolysis and Platelet Aggregation from Snake Venoms: Definition and Nomenclature of Interaction Sites

Abstract

Snake venom metalloproteases, in addition to their contribution to the digestion of the prey, affect various physiological functions by cleaving specific proteins. They exhibit their activities through activation of zymogens of coagulation factors, and precursors of integrins or receptors. Based on their structure-function relationships and mechanism of action, we have defined classification and nomenclature of functional sites of proteases. These metalloproteases are useful as research tools and in diagnosis and treatment of various thrombotic and hemostatic conditions. They also contribute to our understanding of molecular details in the activation of specific factors involved in coagulation, platelet aggregation and matrix biology. This review provides a ready reference for metalloproteases that interfere in blood coagulation, fibrinolysis and platelet aggregation.

Keywords: allosteric sites; anticoagulant; exosites in enzymes; factor X activator; fibrinolytic; platelet aggregation; procoagulant; prothrombin activator.

Figure 1

Snake venom metalloproteases affecting blood coagulation. Proteinases interfere by proteolysis of specific factors (thick arrow heads). Green boxes, procoagulant SVMPs; red box, fibrinogenases that cleave fibrinogen and fibrin; APC, activated protein C; FGDP, fibrinogen degradation products; FnDP, fibrin degradation products; PL, phospholipids; TF, tissue factor; TPA, tissue plasminogen activator; UK, urokinase.

Figure 2

Snake venom metalloproteases affecting platelet aggregation. Proteinases that induce or inhibit platelet aggregation are shown in green or red boxes, respectively; Disintegrins that inhibit platelet aggregation are shown in blue box; PAF, platelet activating factor; PAR, protease activated receptor; PGD, prostaglandin D; PGI, prostaglandin I; TXA2, thromboxane A₂.

Figure 3

Structure of P-III snake venom metalloproteases. All proteins are shown as ribbon structures. Zn²⁺ and Ca²⁺ ions are shown as red and light blue spheres, respectively. Subdomains and segments are colored and named. (A) Catrocollastatin, an inhibitor of collagen-induced platelet aggregation prothrombin activator and a P-III SVMP, showing M, D and C domains, which form a C-shaped configuration (inset). (B) Kaouthiagin-like protease, in contrast exhibits straight configuration. The presence of “hinges” between the domains help P-III SVMPs to “open” and exhibit straighter configuration. (C) Ribbon structure of RVV-X, a P-IIId SVMP. Carinactivase and mutactivase, prothrombin activators, also belong to this class. (D) Docking model (prepared by Soichi Takeda) depicting the structural basis of FX activation.

Figure 4

Nomenclature of interaction sites in snake venom metalloproteases. Left and right columns show free and respective substrate-bound protease. (A) Left: M domain showing catalytic site, prime and non-prime subsites, and proximal allosteric and exosites. Right: Substrate S interacts with the protease through active site and p-exosite. (B) Left: MDC domains showing distal allosteric and exosites. Right: Substrate S interacts with the protease through active site, p-exosite and d-exosite. (C) Left: MDC domains showing distal suresite and adaptor subunit, A showing interaction with MDC domain through distal maresite. A subunit also shows adasite. Right: Substrate S interacts with the protease through active site, p-exosite, d-exosite and adasite. (D) Left: MDC domains showing proximal nedsite. Right: Next-door neighbor (NDN) subunit interacts with p-nedsite, while the substrate S interacts with the protease through active site. See text for details.

Figure 5

Unusual specific binding of snake venom metalloproteases with target receptor. (A) Schematic diagram showing specific binding of active and inactive SVMPs. Diagram is drawn based on the data published by Kamiguti et al. [96]. (B) Active protease cleaves the receptor and gets released into the solution. The picture was created by Cho Yeow Koh and Pol Zen Koh. (C) Inactive protease binds to receptors on the surface of the target cells and remains bound to the cells in the precipitate. (D) Active protease, on the other hand, cleaves the receptor and remains in the supernatant indicating low or no binding to cells in the precipitate.