title: Cytochrome b558: the flavin-binding component of the phagocyte NADPH oxidase.
abstract: The phagocyte respiratory burst oxidase is a flavin-adenine dinucleotide (FAD)-dependent dehydrogenase and an electron transferase that reduces molecular oxygen to superoxide anion, a precursor of microbicidal oxidants. Several proteins required for assembly of the oxidase have been characterized, but the identity of its flavin-binding component has been unclear. Oxidase activity was reconstituted in vitro with only the purified oxidase proteins p47phox, p67phox, Rac-related guanine nucleotide (GTP)-binding proteins, and membrane-bound cytochrome b558. The reconstituted oxidase required added FAD, and FAD binding was localized to cytochrome b558. Alignment of the amino acid sequence of the beta subunit of cytochrome b558 (gp91phox) with other flavoproteins revealed similarities to the nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-binding domains. Thus flavocytochrome b558 is the only obligate electron transporting component of the NADPH oxidase.
authors.affiliation: Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: D
authors.initials: D
authors.lastname: Rotrosen
authors.forename: C L
authors.initials: CL
authors.lastname: Yeung
authors.forename: T L
authors.initials: TL
authors.lastname: Leto
authors.forename: H L
authors.initials: HL
authors.lastname: Malech
authors.forename: C H
authors.initials: CH
authors.lastname: Kwong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002474:Cell-Free System; D003573:Cytochrome b Group / Q000097:blood* / Q000235:genetics / Q000302:isolation & purification; D005287:Ferredoxin-NADP Reductase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007313:Insecta; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000097:blood* / Q000235:genetics / Q000302:isolation & purification; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D010586:Phagocytes / Q000201:enzymology*; D010944:Plants / Q000201:enzymology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013481:Superoxides / Q000097:blood; D014162:Transfection
chemical_list: D003573:Cytochrome b Group; D011994:Recombinant Proteins; D013481:Superoxides; D009249:NADP; C036888:cytochrome b558; D005287:Ferredoxin-NADP Reductase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases