Ibrahim IM, Rowden SJL, Cramer WA, Howe CJ, Puthiyaveetil S. Thiol redox switches regulate the oligomeric state of cyanobacterial Rre1, RpaA, and RpaB response regulators.
FEBS Lett 2022;
596:1533-1543. [PMID:
35353903 PMCID:
PMC9321951 DOI:
10.1002/1873-3468.14340]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/11/2022] [Accepted: 03/16/2022] [Indexed: 11/18/2022]
Abstract
Cyanobacteria employ two‐component sensor‐response regulator systems to monitor and respond to environmental challenges. The response regulators RpaA, RpaB, Rre1 and RppA are integral to circadian clock function and abiotic stress acclimation in cyanobacteria. RpaA, RpaB and Rre1 are known to interact with ferredoxin or thioredoxin, raising the possibility of their thiol regulation. Here, we report that Synechocystis sp. PCC 6803 Rre1, RpaA and RpaB exist as higher‐order oligomers under oxidising conditions and that reduced thioredoxin A converts them to monomers. We further show that these response regulators contain redox‐responsive cysteine residues with an Em7 around −300 mV. These findings suggest a direct thiol modulation of the activity of these response regulators, independent of their cognate sensor kinases.
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