Acid-Sensing Histidine Kinase With a Redox Switch.

Area of Science:

• Microbiology
• Bacterial Physiology
• Signal Transduction

Background:

• The EvgS/EvgA system in Escherichia coli regulates acid resistance genes.
• EvgS, a histidine kinase, has a periplasmic domain for pH sensing and a cytoplasmic PAS domain.
• Previous work suggested the PAS domain's involvement in EvgS activation.

Purpose of the Study:

• To investigate the role of oxygen and ubiquinone in EvgS activation.
• To elucidate the function of the EvgS cytoplasmic PAS domain in signal transduction.

Main Methods:

• EvgS/EvgA reporter assays under varying oxygen conditions.
• Analysis of EvgS mutants (C671A, C683A) in the PAS domain.
• Investigating the requirement of ubiquinone for EvgS activation.

Main Results:

• EvgS activation by mild acidity requires aerobic conditions.
• Mutations in the PAS domain (C671A, C683A) lead to anaerobic EvgS activation.
• Ubiquinone, an electron carrier, is essential for EvgS activation.

Conclusions:

• A model for EvgS activation involving oxidation is proposed.
• The cytoplasmic PAS domain functions as an intermediate redox switch for EvgS activation.