Crystallization and preliminary crystallographic analysis of phosphonoacetaldehyde hydrolase

Phosphonoacetaldehyde hydrolase, a C-P bond-cleaving enzyme which utilizes an unusual bicovalent catalytic strategy, has been crystallized by the hanging-drop vapor-diffusion method using PEG 4000 as the precipitant. The crystals belong to the monoclinic system and belong to space group C2, with unit-cell parameters a = 210.5, b = 45.5, c = 64.7 Å, β = 105.0°. The asymmetric unit contains a dimer related by a non-crystallographic dyad. In addition to a 2.7 Å native data set, the following data sets have been collected: a 2.4 Å data set from crystals complexed with the intermediate analog vinyl sulfonate, a 3.0 Å three-wavelength MAD data set from crystals complexed with the product analog WO₄/^2-, as well as several heavy-atom data sets to 3.0 Å or better, of which only three have proven useful for MIR calculations. Examination of the native Patterson map revealed NCS that made previously uninterpretable derivative data useful. Independent phase sets were first calculated and refined for the MAD and MIR experiments separately and were then combined. The combined phase set was further improved by solvent flattening, histogram matching and NCS averaging. Interpretation of the resulting electron-density map is currently under way.