Change in the conformation of p47phox by sodium dodecyl sulfate, an activator of the leukocyte NADPH oxidase

The leukocyte NADPH oxidase of neutrophils is a membrane-bound enzyme that catalyzes the production of O-2(-) from oxygen using NADPH as an electron donor. Dormant in resting neutrophils, the enzyme acquires catalytic activity when the cells are exposed to appropriate stimuli. During activation, the cytosolic oxidase components p47(phox) and p67(phox) migrate to the plasma membrane, where they associate with cytochrome b(558), a membrane-bound flavohemoprotein, to assemble the active oxidase. The oxidase can be activated in a cell-free system; the activating agent usually employed is an anionic amphiphile such as sodium dodecyl sulfate (SDS), Because p47(phox) can translocate by itself during activation, the conformational change in p47(phox) may be responsible for the activation of NADPH oxidase, We show here that the treatment of p47(phox) With SDS leads to an increase in the reactivity of the sufhydryl group of cysteines toward N-ethylmaleimide, indicating that the conformational change occurs when p47(phox) is exposed to SDS. We propose that this change in conformation results in the appearance of a binding site through which p47(phox) interacts with cytochrome b(558) during the activation process.