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Activation of the phagocyte NADPH oxidase complex requires the assembly of the cytosolic factors p47(PHOX), p67(PHOX), p40(PHOX), and Rac1 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-related functions of Rac1 is to promote the interaction between p67(PHOX) and cytochrome b(558).
Dang et al. (Tue,) studied this question.