A region C-terminal to the proline-rich core of p47^phox regulates activation of the phagocyte NADPH oxidase by interacting with the C-terminal SH3 domain of p67^phox

Activation of the phagocyte NADPH oxidase requires the regulatory proteins p47^phox and p67^phox, each harboring two SH3 domains. p67^phox interacts with p47^phox via simultaneous binding of the p67^phox C-terminal SH3 domain to both the proline-rich region (PRR) of amino acid residues 360-369 and its C-terminally flanking region of p47^phox; the role of the interaction in oxidase regulation has not been fully understood. Here we show that the p47^phox-p67 ^phox interaction is disrupted not only by deletion of the PRR but also by substitution for basic residues in the extra-PRR (K383E/K385E). The substitution impaired oxidase activation partially in vitro and much more profoundly in vivo, indicating the significance of the p47^phox extra-PRR. Replacement of Ser-379 in the extra-PRR, a residue known to undergo phosphorylation in stimulated cells, by aspartate attenuates the interaction and thus results in a defective superoxide production, suggesting that phosphorylation of Ser-379 is involved in oxidase regulation.