Crystallization and preliminary X-ray diffraction analysis of a novel type of phosphoserine phosphatase from Hydrogenobacter thermophilus TK-6

Two novel-type phosphoserine phosphatases (PSPs) with unique substrate specificity from the thermophilic and hydrogen-oxidizing bacterium Hydrogenobacter thermophilus TK-6 have previously been identified. Here, one of the PSPs (iPSP1) was heterologously expressed in Escherichia coli, purified and crystallized. Diffraction-quality crystals were obtained by the sitting-drop vapour-diffusion method using PEG 4000 as the precipitant. Two diffraction data sets with resolution ranges of 45.0-2.50 and 45.0-1.50 Å were collected from a single crystal and were merged to give a highly complete data set. The space group of the crystal was identified as primitive orthorhombic P2₁2₁2₁, with unit-cell parameters a = 49.8, b = 73.6, c = 124.3 Å. The calculated Matthews coefficient (V_M = 2.32 Å³ Da^-1) indicated that the crystal contained one iPSP1 complex per asymmetric unit.