The gp91(phox) component of NADPH oxidase is not the voltage-gated proton channel in phagocytes, but it helps

During the "respiratory burst," the NADPH oxidase complex of phagocytes pro duces reactive oxygen species that kill bacteria and other invaders (Babior , B. M. (1999) Blood 93, 1464-1476). Electron efflux through NADPH oxidase is electrogenic (Henderson, L. M., Chappell, J. B., and Jones, O. T. G. (19 87) Biochem. J. 246, 325-329) and is compensated by H+ efflux through proto n channels that reportedly are contained within the gp91(phox) subunit of N ADPH oxidase. To test whether gp91(phox) functions as a proton channel, we studied H+ currents in granulocytes from X-linked chronic granulomatous dis ease patients lacking gp91(phox) (X-CGD), the human myelocytic PLB-985 cell line, PLB-985 cells in which gp91(phox) was knocked out by gene targeting (PLBKO), and PLB-985 knockout cells re-transfected with gp91(phox) (PLB91). H+ currents in unstimulated PLBKO cells had amplitude and gating kinetics similar to PLB91 cells. Furthermore, stimulation with the phorbol ester pho rbol 12-myristate 13-acetate increased H+ currents to a similar extent in X -CGD, PLBKO, and PLB91 cells. Thus, gp91(phox) is not the proton channel in unstimulated phagocytes and does not directly mediate the increase of prot on conductance during the respiratory burst. Changes in H+ channel gating k inetics during NADPH oxidase activity are likely crucial to the activation of H+ flux during the respiratory burst.