An SH3 domain-mediated interaction between the phagocyte NADPH oxidase factors p40(phox) and p47(phox)

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).