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Thiol redox switches regulate the oligomeric state of cyanobacterial Rre1, RpaA and RpaB response regulators
Iskander M Ibrahim1, Stephen J L Rowden2, William A Cramer3
1Department of Biochemistry and Center for Plant Biology, Purdue University, West Lafayette, IN, USA.
FEBS Letters
|March 30, 2022
Summary
Cyanobacteria response regulators RpaA, RpaB, and Rre1 shift between monomers and oligomers based on redox conditions. This thiol modulation directly impacts their activity, independent of sensor kinases.
Area of Science:
- Molecular Biology
- Cyanobacterial Physiology
- Biochemistry
Background:
- Cyanobacteria utilize two-component systems for environmental sensing and response.
- Key response regulators (RpaA, RpaB, Rre1, RppA) are crucial for circadian rhythms and stress adaptation.
- Previous studies suggested potential thiol regulation for RpaA, RpaB, and Rre1 due to interactions with redox proteins.
Purpose of the Study:
- To investigate the redox-dependent regulation of cyanobacterial response regulators Rre1, RpaA, and RpaB.
- To determine if thiol modulation directly affects the activity of these regulators.
Main Methods:
- Analysis of oligomeric states of Rre1, RpaA, and RpaB under oxidizing and reducing conditions.
- Investigation of the effect of reduced thioredoxin A on the oligomeric state.
- Characterization of redox-responsive cysteine residues and their redox potential (Em7).
Main Results:
- Synechocystis sp. PCC 6803 Rre1, RpaA, and RpaB form higher-order oligomers under oxidizing conditions.
- Reduced thioredoxin A converts these response regulators into monomers.
- Redox-responsive cysteine residues with an Em7 of approximately -300 mV were identified.
Conclusions:
- Direct thiol modulation, independent of sensor kinases, regulates the activity of Rre1, RpaA, and RpaB.
- This redox-based mechanism provides a novel layer of control for cyanobacterial environmental responses.
- Findings highlight the importance of thioredoxin in modulating key cellular processes in cyanobacteria.
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