Crystallization and preliminary X-ray crystallographic analysis of phosphoribulokinase from Rhodobacter sphaeroides

A recombinant form of Rhodobacter sphaeroides phosphoribulokinase (PRK), expressed in Escherichia coli and isolated by affinity chromatography, was crystallized by the sitting drop vapor diffusion technique using NH4H2PO4 (pH 5.6) as the precipitating agent. PRK crystallizes in the cubic space group P432, with unit cell parameters a = b = c = 129.55 A. Based on the assumption of one 32-kDa monomer per asymmetric unit, the Vm value is 2.83 A3/Da. The octameric molecular symmetry is consistent with two planar tetramers stacked in a nearly eclipsed arrangement. A native data set has been collected to 2.6 A resolution.