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

Abstract

The phagocyte NADPH oxidase is activated during phagocytosis to produce superoxide, following assembly of a membrane-integrated cytochrome b ₅₅₈ with cytosolic proteins, p47 ^phox , p67 ^phox and p40 ^phox, each containing Src homology 3 (SH3) domains. While both p47 ^phox and p67 ^phox are indispensable for the oxidase activity, role of p40 ^phox remains obscure. Here we study interaction between p40 ^phox and p47 ^phox 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 p40 ^phox to a C-terminal proline-rich region of p47 ^phox . This proline-rich region is also the target for binding of p67 ^phox , and the SH3 domain of p40 ^phox can inhibit the binding of the C-terminal one of p67 ^phox to p47 ^phox .