The corn inhibitor of blood coagulation factor XIIa. Crystallization and preliminary crystallographic analysis

A 13.6 kDa protein from corn seeds is known to be a highly selective inhibitor of human blood coagulation Factor XIIa (or activated Hageman factor). We have crystallized this inhibitor at 23 degrees C and pH 7.5 from a solution of 30% polyethylene glycol 400, 0.2 M MgCl2, and 0.1 M Hepes. The crystals diffract to at least 2.1 A resolution. The space group is P4(2)2(1)2 with a = b = 57.15 A and c = 80.5 A. The crystals contain 51% solvent. Two heavy atom derivatives have been identified.