Crystallization and preliminary X-ray analysis of the membrane-bound cytochrome c nitrite reductase complex (NrfHA) from Wolinella succinogenes

Crystals of the complex between the enzyme cytochrome c nitrite reductase (NrfA) and the membrane‐bound quinol oxidase and electron carrier NrfH were grown by vapour diffusion using ammonium sulfate as a precipitant. In the ɛ‐proteobacterium Wolinella succinogenes, NrfA and NrfH form a functional membrane‐bound complex which catalyzes the last step in the metabolic pathway of nitrate dissimilation. NrfH represents a prototype of a large family of putative bacterial quinol oxidases, the NapC/NirT family, which have been proposed to serve as electron donors for a variety of reductases. Crystal growth of the NrfHA complex was strongly dependent on the presence of detergent; the crystals grown belonged to space group I422.