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

Activation of the phagocyte NADPH oxidase complex requires the assembly of the cytosolic factors p47(PHOX), P67(PHOX), P40(PHOX), and Rad or Rac2, with the membrane-bound cytochrome b(558) Whereas the interaction of p47(PHOX) with cytochrome b(558) is well established, an interaction between p67(PHOX) and cytochrome b(558) has never been investigated. We report here a direct interaction between p67(PHOX) and cytochrome b(558) First, labeled p67(PHOX) recognizes a 91-kDa band in specific: granules from a normal patient but not from a cytochrome b(558)-deficient patient. Second, p67(PHOX) binds to cytochrome b(558) that has been bound to nitrocellulose. Third, GTP-p67(PHOX) bound to glutathione agarose is able to pull down cytochrome b(558). Rac1-GTP or Rac1-GDP increased the binding of p67(PHOX) to cytochrome b(558), suggesting that at least one of the oxidase-retated functions of Rad is to promote the interaction between p67(PHOX) and cytochrome b(558).