Assembly of the neutrophil respiratory burst oxidase:: A direct interaction between p67PHOX and cytochrome b558 II

Activation of the phagocyte NADPH oxidase complex requires assembly of the cytosolic factors p47(PHOX), p67(PHOX) p40(PHOX) and Rac with the membrane-bound cytochrome b(558). We recently established a direct interaction between p67(PHOX) and cytochrome b(558). In the present study, we show that removal of the C-terminal domain of p67(PHOX) increased its binding to cytochrome b558. Whereas phosphorylated p40(PHOX) alone did not bind to cytochrome b558, phosphorylated p47(PHOX) did, and, moreover, it allowed the binding of p40(PHOX) to the cytochrome. Furthermore, both increased the binding of p67(PHOX) to the cytochrome. Phosphorylated p47(PHOX) thus appears to increase the binding of p67(PHOX) to cytochrome b(558) by serving as an adapter, bringing p67(PHOX) into proximity with cytochrome b558, whereas phosphorylated p40(PHOX) may increase the binding by inducing a conformational change that allows p67(PHOX) to interact fully with cytochrome b(558).