Assembly of the neutrophil respiratory burst oxidase: A direct interactionbetween p67(PHOX) and cytochrome b(558)

Activation of the phagocyte NADPH oxidase complex requires the assembly of the cytosolic factors p47(PHOX), P67(PHOX), P40(PHOX), and Rad or Rac2, wit h the membrane-bound cytochrome b(558) Whereas the interaction of p47(PHOX) with cytochrome b(558) is well established, an interaction between p67(PHO X) and cytochrome b(558) has never been investigated. We report here a dire ct interaction between p67(PHOX) and cytochrome b(558) First, labeled p67(P HOX) recognizes a 91-kDa band in specific: granules from a normal patient b ut 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).