In vivo kinetics of a redox-regulated transcriptional switch.

Department of Molecular and Cellular Toxicology, School of Public Health, Harvard University, 665 Huntington Avenue, Boston, MA 02115-6021, USA.

Proceedings of the National Academy of Sciences of the United States of America 1997 Aug 5

filter terms:

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.

Citation

H Ding, B Demple. In vivo kinetics of a redox-regulated transcriptional switch. Proceedings of the National Academy of Sciences of the United States of America. 1997 Aug 5;94(16):8445-9