Crystallization and preliminary X-ray crystallographic analysis of PdxJ, the pyridoxine 5'-phosphate synthesizing enzyme

The enzyme PdxJ catalyzes the condensation of 1-deoxy-D-xylulose-5-phosphate (DXP) and 1-amino-3-oxo-4-(phosphohydroxy)propan-2-one to form pyridoxine 5'-phosphate (PNP). The protein from Escherichia coli has been crystallized in several forms under different conditions. The best diffracting crystals were obtained by a combination of the hanging-drop vapour-diffusion and microseeding techniques. Using an in-house image plate, the PdxJ crystals diffracted under cryo-conditions to 2.6 Å resolution. The space group has been determined as C222₁, with unit-cell parameters a = 132.5, b = 154.4, c = 131.4 Å, corresponding to four monomers per asymmetric unit. In the search for heavy-atom derivatives, a mercury derivative has been interpreted. The 12 mercury sites located are related by 222 symmetry and, in combination with self-rotation search analyses and gel-filtration experiments, indicate the quaternary assembly of PdxJ into octamers with 422 symmetry.