Crystallization and preliminary X-ray study of alkaline alanine racemase from Bacillus pseudofirmus OF4

Alanine racemase (DadX(OF4)), a dimeric endogenous PLP-dependent alkaline enzyme from alkaliphilic Bacillus pseudofirmus OF4, was expressed in Escherichia coli and purified with a His(6) tag in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop vapour-diffusion method at 291 K using a solution containing 1.4 M sodium/potassium phosphate pH 8.2. The protein crystallized in space group P2(1)2(1)2(1), with two protein molecules in the asymmetric unit.