Purification, crystallization and preliminary X-ray analysis of the soluble domain of the Na+-pumping cytochrome bo quinol oxidase from Vitreoscilla.

The 24 kDa CyoA soluble domain of Vitreoscilla cytochrome bo quinol oxidase, which pumps out Na(+) during respiration, has been crystallized from a solution of 2 M ammonium sulfate and 5% 2-propanol. The crystal belongs to cubic space group P4(3)32, with unit-cell parameters a = b = c = 122.2 A, alpha = beta = gamma = 90 degrees and one subunit in the asymmetric unit. A 99.8% complete data set to 3.3 A has been collected at the 17-ID beamline of the Advanced Photon Source. The structure was determined by molecular replacement and refinement is in progress.