Crystallization and preliminary X-ray analysis of human placental S-adenosylhomocysteine hydrolase

A recombinant form of human placental S-adenosylhomocysteine (AdoHcy) hydrolase expressed in E. coli, which was inactivated by a type-I mechanism-based inhibitor, has been crystallized using the hanging-drop vapour-diffusion technique. The crystals grow as flat plates, with unit-cell dimensions a=96.2, b=173.6, c=142.9 Angstrom alpha=beta=gamma=90 degrees. The crystals exhibit the symmetry of space group C222 and diffract to a minimum spacing of similar or equal to 2.0 Angstrom resolution at the Cornell High Energy Synchrotron Source. On the basis of density calculations two monomers of the tetrameric protein are estimated to be present in the asymmetric unit (V-m = 2.99 Angstrom(3) Da(-1)). The self-rotation function clearly indicates the location of the non-crystallographic twofold axis.