Roles for proline-rich regions of p47phox and p67phox in the phagocyte NADPH oxidase activation in vitro

The cytosolic proteins p47phox and p67phox, each containing two SH3 domains, are required for activation of the superoxide-producing phagocyte NADPH oxidase in a cell-free system with human neutrophil membrane and the small GTPase Rac. Here we focus on roles of proline-rich regions (PRRs) that reside in p47phox and p67phox. Deletion of the p47phox PRR, to which the C-terminal SH3 domain of p67phox binds, results in three-fold decreased activation of the enzyme in the cell-free system with the full-length p67phox, suggesting a modulatory role of the p47phox PRR. The modulation is likely mediated via the C-terminal region of p67phox, since the p47phox mutant protein fully activates the oxidase in combination with the N-terminus of p67phox. Neither deletion of the p67phox PRR nor substitutions for prolines in the region affects the ability to support superoxide production under the cell-free conditions, indicating that the PRR of p67phox has no primary function in the oxidase activation.