Preparation and crystallization of a Bacillus subtilis arsenate reductase

Arsenate reductase (AR) in B. subtilis is encoded by the chromosomal arsC g ene. Together with arsB and arsR, arsC participates in detoxification proce sses for the arsenate and arsenite ions. Full-length arsenate reductase wit hout any modification has been expressed in Escherichia coli and purified i n a soluble form. The recombinant protein has been crystallized at 277 K us ing polyethyleneglycol (PEG) or poly(ethyleneglycol) methyl ether (PME) as the main precipitant. At least two forms of crystals large enough for data collection have been obtained from wild-type protein under different condit ions. An orthorhombic crystal diffracted to beyond 2.2 Angstrom with space group P2(1)2(1)2(1) and unit-cell parameters a = 51.22, b = 91.62, c = 101. 93 Angstrom. A near-complete data set has been collected to 2.5 Angstrom. T he application of the flash-annealing technique was crucial for high resolu tion during the data collection. The SeMet-substituted AR has also been pro duced and crystallized under very similar conditions as the wild type, but the unit-cell parameters are very different. The crystals of the SeMet prot ein diffracted to higher resolution than those of the wild type.