Recombinant form of mammalian gp91^phox is active in the absence of p22^phox

The flavocytochrome b₅₅₈ of the phagocyte NADPH oxidase complex comprises two membrane proteins, a glycosylated gp91^phox and a non-glycosylated p22^phox. Gp91^phox contains all of the redox carriers necessary to reduce molecular oxygen to superoxide using NADPH. The capacity of gp91^phox to produce superoxide in the absence of its membrane partner p22^phox has been little studied. In the present study, we have generated in Pichia pastoris for the first time an active form of bovine gp91^phox able to carry out the entire NADPH oxidase activity in the absence of p22^phox. Collected information on the maturation and the activity of the recombinant gp91^phox and the participation of individual cytosolic subunits in the active complex allowed us to propose, in the absence of p22^phox, an unconventional stabilized complex compared with the heterodimer.