Diffraction quality crystals of protein X from Azotobacter vinelandii

Protein X from Azotobacter vinelandii has recently been shown to be either a NADPH oxidase or a NADP+ reductase that interacts specifically with ferredoxin I. Single crystals have been obtained by vapor diffusion from polyethylene glycol 4000 solutions containing 100 mM citrate buffer (pH 5.5). The crystals belong to space group P2(1)2(1)2 with unit cell constants a = 68.9 A, b = 76.9 A, c = 52.8 A and one molecule (M(r) 29,000) per asymmetric unit. The crystals diffract to 2.5 A resolution.