A reducing system of the superoxide sensor SoxR in Escherichia coli.
The soxRS regulon functions in protecting Escherichia coli cells against superoxide and nitric oxide. When SoxR is activated by oxidation of its [2Fe-2S] cluster, it increases the synthesis of SoxS, which then activates its target gene expression. How the oxidized SoxR returns to and is maintained in its reduced state has been under question. To identity genes that constitute the SoxR-reducing system, we screened an E.coli mutant library carrying a chromosomal soxSp::lacZ fusion, for constitutive mutants. Mutations mapped to two loci: the rsxABCDGE operon (named for reducer of SoxR) that is highly homologous to the rnfABCDGE operon in Rhodobacter capsulatus involved in transferring electrons to nitrogenase, and the rseC gene in the rpoE-rseABC operon. In-frame deletion of each open reading frame in the rsxABCDGE operon produced a similar constitutive phenotype. The double mutation of rsx and rseC suggested that rsxABCDGE and rseC gene products act together in the same pathway in reducing SoxR. Electron paramagnetic resonance analysis of SoxR and measurement of re-reduction kinetics support the proposal that rsx and rseC gene products constitute a reducing system for SoxR.
Koo
Mi-Sun
MS
Laboratory of Molecular Microbiology and Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea.
Lee
Joon-Hee
JH
Rah
So-Yeon
SY
Yeo
Won-Sik
WS
Lee
Jin-Won
JW
Lee
Kang-Lok
KL
Koh
Young-Sang
YS
Kang
Sa-Ouk
SO
Roe
Jung-Hye
JH
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D009876:Operon; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D016354:Rhodobacter capsulatus / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013481:Superoxides / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D014157:Transcription Factors; D013481:Superoxides; C070724:SoxR protein, Bacteria