Cpx-dependent expression of YqjA requires cations at elevated pH

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Escherichia coli must maintain internal pH homeostasis under alkaline environmental conditions.
• Membrane cation/proton (H+) antiporters are crucial for proton influx to counteract alkaline stress.
• The DedA/Tvp38 family protein YqjA is essential for E. coli growth, cell division, and antibiotic resistance.

Purpose of the Study:

• To investigate the role of Escherichia coli YqjA in alkaline pH adaptation.
• To determine the cation dependency of YqjA expression and function.
• To explore the involvement of the Cpx regulon in cation-dependent gene expression at alkaline pH.

Main Methods:

• Utilized a yqjA promoter-lacZ fusion to measure gene expression under varying pH and cation concentrations.
• Assessed bacterial growth and viability under alkaline conditions with different cation supplements.
• Analyzed the transcriptional regulation of yqjA, cpxP, and degP promoters.

Main Results:

• yqjA promoter activity significantly increased at alkaline pH.
• YqjA expression and E. coli viability at alkaline pH were dependent on the presence of sodium or potassium ions.
• Cation-dependent expression of yqjA, cpxP, and degP promoters at alkaline pH was observed, linked to the transcriptional regulator CpxR.

Conclusions:

• Escherichia coli YqjA plays a critical role in surviving alkaline stress, functioning as a cation-dependent transporter.
• Cation availability influences the expression of Cpx-regulated genes, including yqjA, under alkaline conditions.
• This study reveals a novel cation-dependent gene expression mechanism within the Cpx regulon for alkaline pH adaptation in E. coli.