Molecular basis for Rac2 regulation of phagocyte NADPH oxidase.
A Rac GTPase-regulated multiprotein NADPH oxidase is critical for the formation of reactive oxygen species (ROS) in phagocytic leukocytes and other nonphagocytic cells. NADPH oxidase reduces molecular oxygen to form superoxide anion in a two-step process. Electrons are initially transferred from NADPH to cytochrome b-associated FAD, then to cytochrome b heme and finally to molecular oxygen. We show here that Rac is required for both electron-transfer reactions. Mutational and biophysical analysis shows that Rac and p67phox independently regulate cytochrome b to catalyze the transfer of electrons from NADPH to FAD. However, they must interact with each other to induce the subsequent transfer of electrons from FAD to cytochrome b heme and molecular oxygen. This two-step model of regulation by Rac GTPase may provide a means of more effectively controlling the inflammatory responses of phagocytic leukocytes.
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
B A
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Diebold
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Bokoch
D000818:Animals; D003573:Cytochrome b Group / Q000378:metabolism; D004579:Electron Transport; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D010586:Phagocytes / Q000201:enzymology* / Q000276:immunology*; D010750:Phosphoproteins / Q000502:physiology; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000097766:RAC2 GTP-Binding Protein
D003573:Cytochrome b Group; D005182:Flavin-Adenine Dinucleotide; D009249:NADP; D019255:NADPH Oxidases; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; D020744:rac GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein; C079789:neutrophil cytosol factor 67K; C060505:neutrophil cytosolic factor 1