title: FhuF, part of a siderophore-reductase system.
abstract: FhuF is a cytoplasmic 2Fe-2S protein of Escherichia coli loosely associated with the cytoplasmic membrane. E. coli fhuF mutants showed reduced growth on plates with ferrioxamine B as the sole iron source, although siderophore uptake was not defective in transport experiments. Removal of iron from coprogen, ferrichrome, and ferrioxamine B was significantly lower in fhuF mutants compared to the corresponding parental strains, which suggested that FhuF is involved in iron removal from these hydroxamate-type siderophores. A redox potential E(1/2) of -310 +/- 25 mV relative to the normal hydrogen electrode was determined for FhuF by EPR redox titration; this redox potential is sufficient to reduce the siderophores coprogen and ferrichrome. Mössbauer spectra revealed that FhuF in its [Fe(2+)-Fe(3+)] state is also capable of direct reduction of ferrioxamine B-bound ferric iron, thus proving its reductase function. This is the first report on a bacterial siderophore-iron reductase which in vivo seems to be specific for a certain group of hydroxamates.
authors.affiliation: Isotopenlabor TNF, Institut für Biochemie, and Institut für Physik, Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany. matzanke@physik.uni-leubeck.de
authors.forename: Berthold F
authors.initials: BF
authors.lastname: Matzanke
authors.forename: Stefan
authors.initials: S
authors.lastname: Anemüller
authors.forename: Volker
authors.initials: V
authors.lastname: Schünemann
authors.forename: Alfred X
authors.initials: AX
authors.lastname: Trautwein
authors.forename: Klaus
authors.initials: K
authors.lastname: Hantke
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001692:Biological Transport / Q000235:genetics; D003676:Deferoxamine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D005290:Ferric Compounds / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D050895:Nitrate Reductase (NADH); D009565:Nitrate Reductases / Q000737:chemistry*; D010084:Oxidation-Reduction; D033902:Periplasmic Binding Proteins; D017262:Siderophores / Q000737:chemistry*; D015204:Spectroscopy, Mossbauer
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005290:Ferric Compounds; D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D033902:Periplasmic Binding Proteins; D017262:Siderophores; C002577:ferrioxamine B; D007501:Iron; D009565:Nitrate Reductases; D050895:Nitrate Reductase (NADH); D003676:Deferoxamine