In vivo kinetics of a redox-regulated transcriptional switch.
SoxR is a transcription activator governing a cellular response to superoxide and nitric oxide in Escherichia coli. SoxR protein is a homodimer, and each monomer has a redox-active [2Fe-2S] cluster. Oxidation and reduction of the [2Fe-2S] clusters can reversibly activate and inactivate SoxR transcriptional activity. Here, we use electron paramagnetic resonance spectroscopy to follow the redox-switching process of SoxR protein in vivo. SoxR [2Fe-2S] clusters were in the fully reduced state during normal aerobic growth, but were completely oxidized after only 2-min aerobic exposure of the cells to superoxide-generating agents such as paraquat. The oxidized SoxR [2Fe-2S] clusters were rapidly re-reduced in vivo once the oxidative stress was removed. The in vivo kinetics of SoxR [2Fe-2S] cluster oxidation and reduction exactly paralleled the increase and decrease of transcription of soxS, the target gene for SoxR. The kinetic analysis also revealed that an oxidative stress-linked decrease in soxS mRNA stability contributes to the rapid attainment of a new steady state after SoxR activation. Such a redox stress-related change in soxS mRNA stability may represent a new level of biological control.
Ding
H
H
Department of Molecular and Cellular Toxicology, School of Public Health, Harvard University, 665 Huntington Avenue, Boston, MA 02115-6021, USA.
Demple
B
B
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D014157:Transcription Factors; C070724:SoxR protein, Bacteria