The respiratory burst oxidase of phagocytes and B lymphocytes catalyzes the reduction of oxygen by NADPH to form O2-, the precursor of a group of reactive oxidants that are employed by phagocytes as microbicidal agents. The enzyme is active in stimulated cells but dominant in resting cells. It molecular weight guanine nucleotide-binding protein. The components p22phox and gp91phox from cytochrome b558, a flavohemoprotein that resides in the cortical cytoskeleton and in the membranes of the specific granules. The other components are found in the cytosol of resting cells, but migrate to the cortical cytoskeleton when the neutrophils are activated, where they assemble the active oxidase. Migration to the cortical cytoskeleton is caused in part by the appearance of a membrane binding site on one or more of the cytosolic subunits, possibly due to the phosphorylation of p47phox that takes place during cell activation.