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 conv entional techniques and crystallized by the hanging-drop vapour-diffusion m ethod using sodium citrate as the precipitant. Two crystal forms representi ng the free enzyme and the binary complex with NADP(+) grow under these con ditions. Crystals of form I diffract to beyond 3.5 Angstrom resolution and belong to the hexagonal space group P622, with unit-cell parameters a=b=89. 1, c=214.6 Angstrom, alpha=beta =90, gamma =120 degrees. Crystals of form I I diffract to greater than 2.0 Angstrom and belong to the orthorhombic spac e group I222 or I2(1)2(1)2(1), with unit-cell parameters a=61.8, b=110.9, c =151.7 Angstrom, alpha=beta=gamma =90 degrees. Calculated values for V-M an d consideration of the packing for both crystal forms suggests that the asy mmetric units in both crystal forms contain a monomer.