Ferric iron reductase

Seeliger S, R Cord-Ruwisch B Schink (1998) A periplasmic and extracellular c-type cytochrome of Geobacter sulfurreducens acts as a ferric iron reductase and as an electron carried to other acceptors or to partner bacteria. J Bacteriol 180 3686-3691. 

It has been suggested that membrane ferric iron reductases are involved in, and perhaps even essential for, NTBI uptake and acquisition by cells (Inman and Wessling-Resnick, 1993 Randell et al., 1994). A novel factor involved in cellular iron... 

Liger D, Graille M, Zhou CZ, Leulliot N, Quevillon-Chemel S, Blondeau K, Janin J, van Tilbeurgh H (2004) Crystal structure and functional characterization of yeast YLROllwp, an enzyme with NAD(P)H-FMN and ferric iron reductase activities. J Biol... 

Schroder I, Johnson E, de Vries S. Microbial ferric iron reductases. 45. EEMS Microbiol. Rev. 2003 27 427-447. 

A membrane-bound NADH-dependent ferric iron reductase has been obtained from Geobacter sulfurreducens (Magnuson et al., 2000). The enzyme contains a hemoprotein and FAD. the reduced hemoprotein in the enzyme is reoxidized on addition of ferric ion and NADH is a specific electron donor for the enzyme. The bacterium has a citric acid cycle (TCA cycle) (Galushko and Schink, 2000). Besides G. metallireducens and G. sulfurreducens, several bacteria of Geobacter genus have been isolated, namely G. bremensis, G. pelophilus (Straub and Buchholz-Cleven, 2001), G. hydrogenophilus, G. chapelli, and G. grbiciae (Coates et al., 2001). 

Schroder, 1., E. Johnson, and S. de Vries. 2003. Microbial ferric iron reductases. FEMS Microbiology Reviews 27(2-3) 427-447. 

Fontecave M, Ehasson R, Reichard P. 1987. NAD(P)H-flavin oxidoreductase of Escherichia coli a ferric iron reductase participating in the generation of the free-radical ofribonucleotide reductase. J Rio/ Chem 262 12325—12331. 

The iron of Hb must be maintained in the ferrous state ferric iron is reduced to the ferrous state by the action of an NADH-dependent methemoglobin reductase system involving cytochrome reductase and cytochrome b. ... 

There is some evidence that the iron-sulfur protein, FhuF, participates in the mobilization of iron from hydroxamate siderophores in E. coli (Muller et ah, 1998 Hantke, K. unpublished observations). However, a reductase activity of FhuF has not been demonstrated. Many siderophore-iron reductases have been shown to be active in vitro and some have been purified. The characterization of these reductases has revealed them to be flavin reductases which obtain the electrons for flavin reduction from NAD(P)H, and whose main functions are in areas other than reduction of ferric iron (e.g. flavin reductase Fre, sulfite reductase). To date, no specialized siderophore-iron reductases have been identified. It has been suggested that the reduced flavins from flavin oxidoreductases are the electron donors for ferric iron reduction (Fontecave et ah, 1994). Recently it has been shown, after a fruitless search for a reducing enzyme, that reduction of Co3+ in cobalamin is achieved by reduced flavin. Also in this case it was suggested that cobalamins and corrinoids are reduced in vivo by flavins which may be generated by the flavin... 

As we saw in the previous section, Strategy 1 plants utilize ferric reductases, with NADPH as electron donor, coupled to proton extrusion and a specific Fe(II) transport system localized in the root plasma membrane. Saccharomyces cerevisiae also uses cell surface reductases to reduce ferric iron, and in early studies (Lesuisse et ah, 1987 ... 

Campbell, W.H. Redinbaugh, M.G. (1984). Ferric-citrate reductase activity of nitrate reductase and its role in iron assimilation by plants. Journal of Plant Nutrition 7, 799-806. 

The physiological roles of the phenolates produced by B. thuringien-sis are not known. Neither the slow band nor the intermediate band serves as the molybdenum cofactor in the in vitro restoration of NADPH-nitrate reductase. It is reasonable nevertheless to posulate that these compounds are excreted by this organism in nature and that under the appropriate environmental conditions, these phenolates will coordinate tungstate, ferric iron, or molybdate. 

Figure 3. Diagram of a section through the cell wall of Acidithiobacillus ferrooxidans modified from Blake et al. (1992) showing the relationship between iron oxidation and pyrite dissolution. OM =outer membrane, P = periplasm, IM = inner or (cytoplasmic) membrane, cty = cytochrome, pmf = proton motive force. Passage of a proton (driven by proton motive force) into the cell catalyzes the conversion of ADP to ATP. Ferrous iron binds to a component of the electron transport chain, probably a cytochrome c, and is oxidized. The electrons are passed to a terminal reductase where they are combined with O2 and to form water, preventing acidification of the cytoplasm. Ferric iron can either oxidize pyrite (e.g. within the ore body) or form nanocrystalline iron oxyhydroxide minerals (often in surrounding groundwater or streams).

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