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 produc e superoxide, following assembly of a membrane-integrated cytochrome b (558) with cytosolic proteins, p47(phox), p67(phox) and p40(phox), eac h containing Src homology 3 (SH3) domains, While both p47(phox) and p6 7(phox) are indispensable for the oxidase activity, role of p40(phox) remains obscure, Here we study interaction between p40(phox) and p47(p hox) 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 o f p40(phox) to a C-terminal proline-rich region of p47(phox), This pro line-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).