Assembly of the neutrophil respiratory burst oxidase: A direct interaction between p67 PHOX and cytochrome b 558 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 b 558 . Whereas phosphorylated p40 PHOX alone did not bind to cytochrome b 558 , 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 b 558 , whereas phosphorylated p40 PHOX may increase the binding by inducing a conformational change that allows p67 PHOX to interact fully with cytochrome b 558 .