Coagulation factor II, also known as F2, is proteolytically cleaved to form thrombin in the first step of the coagulation cascade which ultimately results in the stemming of blood loss. F2 also plays a role in maintaining vascular integrity during development and postnatal life. Mutations in F2 lead to various forms of thrombosis and dysprothrombinemia. Recombinant human F2 protein was expressed in E.coli.