Crystallization and preliminary X-ray studies of Pseudomonas putida histidine ammonium-lyase

Histidine ammonium-lyase from P. putida was expressed in Escherichia coli, purified to homogeneity, and crystallized by the vapour-diffusion method using polyethylene glycol 3350 as the precipitant. The crystals, which diffract to at least 2.5 Å resolution, exhibit the symmetry of space group P2₁2₁2₁, with unit-cell parameters a = 89.7, b = 138.2 and c = 164.8 Å. The asymmetric unit contains a tetramer, and the crystals have a V_m value of 2.41 Å³ Da^-1.