Characterization and Preliminary Crystallographic Studies of EMS 16, an Antagonist of Collagen Receptor (GPIa/IIa) from the Venom of Echis multisquamatus

Abstract

EMS 16 is a member of the snake venom-derived C-type lectin family of proteins (CLPs) found in the venom of Echis multisquamatus. It binds to glycoprotein Ia/IIa (integrin α2β1), a major collagen receptor of platelets, acting as a potent antagonist of platelet aggregation and cell migration. Amino acid sequencing and cDNA cloning of EMS 16 have revealed that it is composed of an A chain of 134 amino acid residues and a B chain of 128 residues. Crystals of EMS 16 belong to space group P2₁2₁2₁, with unitcell parameters a=46.57, b=59.93, and c=115.74 Å, and diffract to a resolution of 1.9 Å. Phase determination is underway by means of molecular replacement with the structure of blood coagulation factor IX-binding protein (IX-bp) from habu snake venom (PDB code 1bj3) as the search model.