Phosphorylation induces conformational changes in the leukocyte NADPH oxidase subunit p47(phox)

The leukocyte NADPH oxidase of neutrophils is a membrane-bound enzyme that catalyzes the reduction of oxygen to at the expense of NADPH. The enzyme is dormant in resting neutrophils but becomes active when the cells are exposed to appropriate stimuli. During oxidase activation, the highly basic cytosolic oxidase component p47(phox) becomes phosphorylated on several serines and migrates to the plasma membrane. We report here that phosphorylation of p47(phox) with protein kinase C induces conformational changes, as reflected by a fluorescence change of N, N'-di-methyl-N(iodoacetyl)-N'-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) ethyleneamine (IANBD)-labeled p47(phox). We propose that this alteration in conformation results in the appearance of a binding site through which p47(phox) interacts with cytochrome b558 during the activation process. In addition, the present study indicates that other oxidase components, such as p67(phox) and p22(phox), influence the conformation of p47(phox).