title: Overproduction and physical characterization of SoxR, a [2Fe-2S] protein that governs an oxidative response regulon in Escherichia coli.
abstract: SoxR protein governs the soxRS (superoxide response) regulon of Escherichia coli by becoming a transcriptional activator when the cells are exposed to compounds that mediate univalent redox reactions, many of which produce superoxide as a by-product. SoxR was overproduced and purified to near homogeneity from a strain bearing an expression vector. It could bind specifically to the soxS operator even in the absence of RNA polymerase. The aerobically purified protein, which is readily autooxidized, could activate the transcription of soxS DNA even without exposure to known inducing agents. SoxR is a globular homodimer. It contains one [2Fe-2S] cluster per polypeptide chain, as demonstrated by optical and EPR spectroscopy combined with stoichiometric analysis of iron content, unpaired-electron-spin density, and reduction by dithionite. The protein is active in its oxidized ([2Fe-2S]2+) state. The presence of a prosthetic group capable of univalent redox reactions may help to explain the activation of the regulon in vivo by compounds that can mediate such reactions.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor 48109-0602, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: W R
authors.initials: WR
authors.lastname: Dunham
authors.forename: B
authors.initials: B
authors.lastname: Weiss
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004227:Dithionite / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D008670:Metals / Q000032:analysis; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010957:Plasmids; D018085:Regulon; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D007506:Iron-Sulfur Proteins; D008670:Metals; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; D004227:Dithionite