Preliminary X-ray crystallographic analysis of Tritrichomonas foetus inosine-5'-monophosphate dehydrogenase

Inosine-5'-monophosphate dehydrogenase (IMPDH) from the protozoan parasite Tritrichomonas foetus has been expressed in E. coli and crystallized. Crystals were grown to 0.1 mm in each dimension in 18 to 72 h using ammonium sulfate and low-molecular-weight polyethylene glycols. The crystals belong to the cubic space group P432 with unit cell edge = 157.25 A. The enzyme is a homotetramer with each monomer having a molecular weight of 55,534 Da. There is one monomer per asymmetric unit, based on a volume/mass ratio of 2.7 A3/Da and self-rotation analysis. The crystals are adequately stable to allow a complete data set to be collected from a single crystal. Complete native data sets have been collected to 2.3 A resolution at 4 degrees C using synchrotron radiation. High-quality complete data extending to 3.0 A resolution have been collected from crystals of four putative derivatives, and the data appear to be isomorphous with that of the native crystals in each case. Efforts to solve the derivatives for use in MIR phasing are underway.