Molecular characterization and anticoagulant activity of a novel annexin derived from the Taenia solium

A novel annexin gene was isolated from the Taenia solium cDNA library by degenerate PCR. The purified protein was generated by hydrolysis with thrombin in glutathione S-transferase (GST) affinity chromatography following expression in GST tagged pGEX-5T vector. It shares the common structural features of the annexin family and specially possesses two unique fragments between repeating domains II and III which do not exist in other annexin family members revealed by aligning and homology modeling, hence it was designated as Tso ANXB2 according to the new nomenclature of annexins. According to the parasitic behaviors of the origin, a series of coagulation assays was performed, indicating that Tso ANXB2 inhibits extrinsic blood coagulation pathway and platelet aggregation also has platelet binding activity. Nevertheless, the mutant protein deleting the consensus coagulation-related KGD motif of Tso ANXB2 showed significant decreasing platelet binding and anticoagulation activity.