Model of NADPH oxidase assembly. Activation/phosphorylation (P)-induced conformational changes in p47^phox release autoinhibitory interactions to unmask essential binding domains and exposure of PX domains that facilitate membrane targeting and binding of SH3-mediated and non–SH3-mediated binding events. Final interaction of the p67^phox and Rac with flavocytochrome b induces conformational change, resulting in electron flow. Illustration by Kenneth Probst. Adapted with permission from Journal of Leukocyte Biology. Quinn MT, Gauss KA. Structure and regulation of the neutrophil respiratory burst oxidase: comparison with nonphagocyte oxidases. J Leukoc Biol. 2004;76:760-781.⁷¹