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Updated: May 7, 2026
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EPR Monitored Redox Titration of the Cofactors of Saccharomyces cerevisiae Nar1
Published on: November 26, 2014
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Comparative study of SoxR activation by redox-active compounds.
Atul K Singh1, Jung-Ho Shin, Kang-Lok Lee
1Laboratory of Molecular Microbiology, School of Biological Sciences, Institute of Microbiology, Seoul National University, Seoul, 151-747, Korea.
Molecular Microbiology
|October 12, 2013
Summary
SoxR proteins from different bacteria show varied responses to redox compounds. Differences in redox potential and reactivity explain why some SoxRs are more sensitive to oxidants than others.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- SoxR regulates gene expression in response to redox-active compounds.
- Enteric SoxR (EcSoxR) activates SoxS, which then induces over 100 genes.
- Non-enteric SoxRs directly activate target genes.
Purpose of the Study:
- Compare the responsiveness of SoxR from Streptomyces coelicolor (ScSoxR), Pseudomonas aeruginosa (PaSoxR), and E. coli (EcSoxR).
- Investigate the impact of redox potential and kinetic reactivity on SoxR activation.
Main Methods:
- Expressing different SoxRs in S. coelicolor and E. coli.
- Testing responsiveness to various natural and synthetic redox-active compounds.
- Utilizing whole-cell Electron Paramagnetic Resonance (EPR) spectroscopy.
- Determining the mid-point redox potential of purified ScSoxR.
Main Results:
- EcSoxR responded to all tested compounds.
- ScSoxR was insensitive to certain oxidants and NO generators.
- PaSoxR showed partial insensitivity to NO generators.
- ScSoxR's [2Fe-2S](1+) cluster was not oxidizable by paraquat, unlike EcSoxR and PaSoxR.
- ScSoxR has a higher mid-point redox potential (-185 ± 10 mV) compared to EcSoxR and PaSoxR.
Conclusions:
- Differential sensitivity of SoxRs is influenced by both redox potential and kinetic reactivity.
- ScSoxR's higher redox potential contributes to its limited response to oxidants like paraquat.
- Understanding these differences is crucial for comprehending bacterial redox stress response mechanisms.
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