Expression, purification, crystallization and preliminary crystallographic analysis of phosphoserine aminotransferase from Bacillus alcalophilus

Phosphoserine aminotransferase (PSAT; EC 2.6.1.52) from Bacillus alcalophilus, an obligatory alkalophile with optimum growth at pH 10.6, was overexpressed in Escherichia coli, purified and crystallized under two different conditions using the hanging‐drop vapour‐diffusion method. Crystals were obtained using trisodium citrate dihydrate or PEG 400 as a precipitating agent. Crystals grown in the presence of trisodium citrate belong to the orthorhombic space group C2221, with unit‐cell parameters a = 105.6, b = 136.6, c = 152.0 Å, and those grown in the presence of PEG 400 belong to the orthorhombic space group P21212, with unit‐cell parameters a = 143.7, b = 84.3, c = 67.4 Å. Complete data sets were collected to 1.7 and 1.6 Å resolution, respectively, at 100 K using synchrotron radiation. Analysis of the structure of B. alcalophilus PSAT may reveal structural features that contribute to enzyme adaptability at high pH values.