Crystallization and preliminary X-ray analysis of glucose dehydrogenase from Haloferax mediterranei

Glucose dehydrogenase (E.C 1.1.1.47; GlcDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized by the addition of 8 M urea and refolded by rapid dilution. The protein has been purified by conventional techniques and crystallized by the hanging‐drop vapour‐diffusion method using sodium citrate as the precipitant. Two crystal forms representing the free enzyme and the binary complex with NADP+ grow under these conditions. Crystals of form I diffract to beyond 3.5 Å resolution and belong to the hexagonal space group P622, with unit‐cell parameters a = b = 89.1, c = 214.6 Å, α = β = 90, γ = 120°. Crystals of form II diffract to greater than 2.0 Å and belong to the orthorhombic space group I222 or I212121, with unit‐cell parameters a = 61.8, b = 110.9, c = 151.7 Å, α = β = γ = 90°. Calculated values for VM and consideration of the packing for both crystal forms suggests that the asymmetric units in both crystal forms contain a monomer.