Purification, crystallization and preliminary crystallographic analysis of a dissimilatory DsrAB sulfite reductase in complex with DsrC

Dissimilatory sulfite reductase (dSiR, DsrAB) is a key protein in dissimilatory sulfur metabolism, one of the earliest types of energy metabolism to be traced on earth. dSirs are large oligomeric proteins around 200 kDa forming an α2β2 arrangement and including a unique siroheme-[4Fe–4S] coupled cofactor. Here, we report the purification, crystallization and preliminary X-ray diffraction analysis of dSir isolated from Desulfovibrio vulgaris Hildenborough, also known as desulfoviridin. In this enzyme the DsrAB protein is associated with DsrC, a protein of unknown function that is believed to play an important role in the sulfite reduction. Crystals belong to the monoclinic space group P21 with unit-cell parameters a = 122.7, b = 119.4 and c = 146.7 Å and β =110.0°, and diffract X-rays to 2.8 Å on a synchrotron source.