title: Characterization of the quinone reductase activity of the ferric reductase B protein from Paracoccus denitrificans.
abstract: The ferric reductase B (FerB) protein of Paracoccus denitrificans exhibits activity of an NAD(P)H: Fe(III) chelate, chromate and quinone oxidoreductase. Sequence analysis places FerB in a family of soluble flavin-containing quinone reductases. The enzyme reduces a range of quinone substrates, including derivatives of 1,4-benzoquinone and 1,2- and 1,4-naphthoquinone, via a ping-pong kinetic mechanism. Dicoumarol and Cibacron Blue 3GA are competitive inhibitors of NADH oxidation. In the case of benzoquinones, FerB apparently acts through a two-electron transfer process, whereas in the case of naphthoquinones, one-electron reduction takes place resulting in the formation of semiquinone radicals. A ferB mutant strain exhibited an increased resistance to 1,4-naphthoquinone, attributable to the absence of the FerB-mediated redox cycling. The ferB promoter displayed a high basal activity throughout the growth of P. denitrificans, which could not be further enhanced by addition of different types of naphthoquinones. This indicates that the ferB gene is expressed constitutively.
authors.affiliation: Department of Biochemistry, Masaryk University, Brno, Czech Republic.
authors.forename: Vojtech
authors.initials: V
authors.lastname: Sedlácek
authors.forename: Rob J M
authors.initials: RJ
authors.lastname: van Spanning
authors.forename: Igor
authors.initials: I
authors.lastname: Kucera
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D038181:FMN Reductase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010231:Paracoccus denitrificans / Q000201:enzymology* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011809:Quinones / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D011809:Quinones; D011993:Recombinant Fusion Proteins; D038181:FMN Reductase; D016660:NAD(P)H Dehydrogenase (Quinone); C023903:ferric citrate iron reductase