Recombinant Pseudonaja textilis Venom prothrombin activator pseutarin-C catalytic subunit

Snake prothrombin activator that attacks the hemostatic system of prey. This non-catalytic subunit is functionally similar to blood coagulation factor V. It serves as a critical cofactor for the prothrombinase activity of the catalytic subunit, which is similar to the blood coagulation factor X. The complex converts prothrombin to thrombin by sequential cleavage at two positions, Arg-320 followed by Arg-271. Cleavage at Arg-320 produces an active intermediate known as meizothrombin. Meizothrombin is the 'second' substrate for prothrombinase, and it docks in an altered manner to present the second cleavage site (271). Cleavage at Arg-271 releases active thrombin from its pro-fragment. This order of events is reversed if the protease component of prothrombinase is used on its own, suggesting that the 271 site is inherently more accessible to proteolysis. The complex converts prothrombin to thrombin in presence but also in the absence of membrane.