Crystallization and initial X-ray diffraction studies of the flavoenzyme NAD(P)H:(acceptor) oxidoreductase (FerB) from the soil bacterium Paracoccus denitrificans.

The flavin-dependent enzyme FerB from Paracoccus denitrificans reduces a broad range of compounds, including ferric complexes, chromate and most notably quinones, at the expense of the reduced nicotinamide adenine dinucleotide cofactors NADH or NADPH. Recombinant unmodified and SeMet-substituted FerB were crystallized under similar conditions by the hanging-drop vapour-diffusion method with microseeding using PEG 4000 as the precipitant. FerB crystallized in several different crystal forms, some of which diffracted to approximately 1.8 A resolution. The crystals of native FerB belonged to space group P2(1), with unit-cell parameters a = 61.6, b = 110.1, c = 65.2 A, beta = 118.2 degrees and four protein molecules in the asymmetric unit, whilst the SeMet-substituted form crystallized in space group P2(1)2(1)2, with unit-cell parameters a = 61.2, b = 89.2, c = 71.5 A and two protein molecules in the asymmetric unit. Structure determination by the three-wavelength MAD/MRSAD method is now in progress.