An SH3 domain‐mediated interaction between the phagocyte NADPH oxidase factors p40phox and p47phox

The phagocyte NADPH oxidase is activated during phagocytosis to produce superoxide, following assembly of a membrane-integrated cytochrome b558 with cytosolic proteins, p47phox, p67phox and p40phox, each containing Src homology 3 (SH3) domains. While both p47phox and p67phox are indispensable for the oxidase activity, role of p40phox remains obscure. Here we study interaction between p40phox and p47phox by two independent methods, a two-hybrid system in the yeast and an in vitro binding assay using purified proteins. The present results show that the interaction is mediated via binding of the SH3 domain of p40phox to a C-terminal proline-rich region of p47phox. This proline-rich region is also the target for binding of p67phox, and the SH3 domain of p40phox can inhibit the binding of the C-terminal one of p67phox to p47phox.