Preparation and crystallization of a Bacillus subtilis arsenate reductase

Arsenate reductase (AR) in B. subtilis is encoded by the chromosomal arsC gene. Together with arsB and arsR, arsC participates in detoxification processes for the arsenate and arsenite ions. Full-length arsenate reductase without any modification has been expressed in Escherichia coli and purified in a soluble form. The recombinant protein has been crystallized at 277 K using 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 conditions. An orthorhombic crystal diffracted to beyond 2.2 Å with space group P212121 and unit-cell parameters a = 51.22, b = 91.62, c = 101.93 Å. A near-complete data set has been collected to 2.5 Å. The application of the flash-annealing technique was crucial for high resolution during the data collection. The SeMet-substituted AR has also been produced and crystallized under very similar conditions as the wild type, but the unit-cell parameters are very different. The crystals of the SeMet protein diffracted to higher resolution than those of the wild type.