Crystallization and preliminary X-ray analysis of D-­2-hydroxyacid dehydrogenase from Haloferax mediterranei

D-2-Hydroxyacid dehydrogenase (D2-HDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized in 8 M urea and refolded by rapid dilution. The protein was purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate or PEG 3350 as precipitant. Two crystal forms representing the free enzyme and the non­productive ternary complex with α-ketohexanoic acid and NAD⁺ grew under these conditions. Crystals of form I diffracted to beyond 3.0 Å resolution and belonged to the monoclinic space group P2₁, with unit-cell parameters a = 66.0, b = 119.6, c = 86.2 Å, β = 96.3°. Crystals of form II diffracted to beyond 2.0 Å resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 66.5, b = 75.2, c = 77.6 Å, α = 109.1, β = 107.5, γ = 95.9°. The calculated values for V_M and analysis of the self-rotation and self-Patterson functions suggest that the asymmetric unit in both crystal forms contains two dimers related by pseudo-translational symmetry.