Effect of positive redox potentials (greater than +400 mV) on the expression of anaerobic respiratory enzymes in Escherichia coli.
The expression of fumarate reductase and other enzymes of anaerobic respiration in Escherichia coli was studied as a function of the redox potential (Eh) in the medium. Redox potentials up to +300 mV allowed full expression of fumarate reductase (frd) genes. Higher values resulted in decreased expression. The relationship between Eh and expression of frd could be approximated by the Nernst equation, assuming a redox couple with a midpoint potential Eo' = +400 mV to 440 mV. At Eh values greater than +510 mV (generated anaerobically by hexacyanoferrate(III] the degree of repression was the same as that obtained by O2. Hexacyanoferrate(III) also caused decreased activities of dimethylsulphoxide (DMSO), nitrite and nitrate reductases. Since expression of these enzymes depends on FNR, the gene activator of anaerobic respiratory genes, it is suggested that the function of FNR is controlled by a redox couple of Eo' = +400 mV to 440 mV.
Institut für Mikrobiologie, J. W. Goethe-Universität, Frankfurt, FRG.
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D000693:Anaerobiosis / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005292:Ferricyanides / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007506:Iron-Sulfur Proteins; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000096:biosynthesis*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010100:Oxygen / Q000502:physiology
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D005292:Ferricyanides; D007506:Iron-Sulfur Proteins; C007931:hexacyanoferrate III; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C020155:fumarate reductase (NADH); D010100:Oxygen