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The Response Regulator RegA Is a Copper Binding Protein That Covalently Dimerizes When Exposed to Oxygen
1Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA.
Microorganisms
|May 28, 2022
Summary
Copper binding to RegA protein in Rhodobacter capsulatus promotes its dimerization under aerobic conditions, enabling gene regulation. This discovery reveals a new mechanism for aerobic gene expression control.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- The transcriptional factor RegA in Rhodobacter capsulatus is known to regulate genes under anaerobic conditions.
- Transcriptome data suggests RegA also plays a role in aerobic gene regulation, contradicting previous understanding.
Purpose of the Study:
- To investigate the mechanism of aerobic gene regulation by RegA.
- To determine if copper influences RegA activity under aerobic conditions.
Main Methods:
- Inductively coupled plasma mass spectrometry (ICP-MS) to quantify copper binding.
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and electrospray ionization mass spectrometry (ESI-MS) to analyze protein modifications.
- Non-reducing SDS-PAGE to detect disulfide bond formation.
- DNase I footprint analysis to assess promoter binding.
Main Results:
- RegA was identified as a copper-binding protein, with distinct binding ratios for Cu 1+ and Cu 2+ .
- Cu 2+ in the presence of oxygen stimulates the formation of an intermolecular disulfide bond at Cys156 in RegA.
- The Cu 2+ -mediated dimerized RegA binds to the ccoN promoter, regulating cytochrome cbb3 oxidase gene expression.
Conclusions:
- A novel model for aerobic gene regulation by RegA is proposed, involving copper-mediated dimerization via disulfide bond formation.
- This mechanism highlights the role of copper in coordinating gene expression in response to oxygen availability.
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