FhuF, part of a siderophore-reductase system |
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Authors: | Matzanke Berthold F Anemüller Stefan Schünemann Volker Trautwein Alfred X Hantke Klaus |
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Institution: | Isotopenlabor TNF, Institut für Biochemie, and Institut für Physik, Universit?t zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany. matzanke@physik.uni-leubeck.de |
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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. M?ssbauer 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. |
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