Crystallization and preliminary X-ray analysis of human antithrombin III

Human antithrombin III has been crystallized from 18 to 21% (w/v) polyethylene glycol 4000 at pH 7.15. The spacegroup is P2(1) with cell parameters a = 89.8 A, b = 100.8 A, c = 70.0 A and beta = 106 degrees. The diffraction limit is 3.2 A. The asymmetric unit contains two protein molecules. Analysis of dissolved crystals for biological activity and by gel electrophoresis suggests that one protein molecule in the asymmetric unit is intact, while the other is cleaved.