Abstact

The three-dimensional structure of glycosomal glyceraldehyde-3-phosphate dehydrogenase [D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.12.1.12] from the sleeping-sickness parasite Trypanosoma brucei was solved by molecular replacement at 3.2-A resolution with an x-ray data set collected by the Laue method. For data collection, three crystals were exposed to the polychromatic synchrotron x-ray beam for a total of 20.5 sec. The structure was solved by using the Bacillus stearothermophilus enzyme model [Skarzyński, T., Moody, P. C. E. & Wonacott, A. J. (1987) J. Mol. Biol. 193, 171-187] with a partial data set which was 37% complete. The crystals contain six subunits per asymmetric unit, which allowed us to overcome the absence of > 60% of the reflections by 6-fold density averaging. After molecular dynamics refinement, the current molecular model has an R factor of 17.6%. Comparing the structure of the trypanosome enzyme with that of the homologous human muscle enzyme, which was determined at 2.4-A resolution, reveals important structural differences in the NAD binding region. These are of great interest for the design of specific inhibitors of the parasite enzyme.