title: Binding of promoter DNA to SoxR protein decreases the reduction potential of the [2Fe-2S] cluster.
abstract: The [2Fe-2S] transcriptional factor SoxR, a member of the MerR family, functions as a sensor of oxidative stress in Escherichia coli. The transcriptional activity of SoxR is regulated by the reversible oxidation and reduction of [2Fe-2S] clusters. Electrochemistry measurements on DNA-modified electrodes have shown a dramatic shift in the reduction potential of SoxR from -290 to +200 mV with the promoter DNA-bound [ Gorodetsky , A. A. , Dietrich , L. E. P. , Lee , P. E. , Demple , B. , , Newman , D. K. , and Barton , J. K. ( 2008 ) DNA binding shifts the reduction potential of the transcription factor SoxR , Proc. Natl. Acad. Sci. U.S.A. 105 , 3684 - 3689 ]. To determine the change of the SoxR reduction potential using the new condition, the one-electron oxidation-reduction properties of [2Fe-2S] cluster in SoxR were investigated in the absence and presence of the DNA. The [2Fe-2S] cluster of SoxR was completely reduced by nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P450 reductase (CRP) in the presence of a NADPH generating system (glucose 6-dehydrogenase and glucose-6 phosphate), indicating that CRP can serve as an NADPH-dependent electron carrier for SoxR. The reduction potential of SoxR was measured from equilibrium data coupled with NADPH and CRP in the presence of electron mediators. The reduction potentials of DNA-bound and DNA-free states of SoxR were -320 and -293 mV versus NHE (normal hydrogen electrode), respectively. These results indicate that DNA binding causes a moderate shift in the reduction potential of SoxR.
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Mayu
authors.initials: M
authors.lastname: Fujikawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kozawa
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007506:Iron-Sulfur Proteins; D014157:Transcription Factors; C070724:SoxR protein, Bacteria