Crystallization and preliminary crystallographic analysis of p40 ^phox, a regulatory subunit of NADPH oxidase

p40^phox is a cytosolic component of the phagocyte NADPH oxidase, which is responsible for production of the superoxide that kills invasive microorganisms. Full-length p40^phox was expressed in Escherichia coli, purified and crystallized by the sitting-drop vapour-diffusion method at 293 K using polyethylene glycol 20 000 as a precipitant. Diffraction data were collected to 3.0 Å resolution at 100 K using synchrotron radiation. The crystal belongs to space group C222₁, with unit-cell parameters a = 146.27, b = 189.81, c = 79.88 Å. This crystal was estimated to contain two or three protein molecules per asymmetric unit from the acceptable range of volume-to-weight ratio values.