Structural dependence of ProQ-mRNA interactions in live bacterial cells

Area of Science:

• Bacteriology
• Molecular Biology
• Gene Regulation

Background:

• ProQ is a bacterial post-transcriptional regulator interacting with both messenger RNAs (mRNAs) and small regulatory RNAs (sRNAs).
• Understanding ProQ's specific interactions with mRNAs is crucial for deciphering gene regulation mechanisms.

Purpose of the Study:

• To investigate ProQ-mRNA interactions in live bacteria using advanced single-molecule tracking.
• To determine the influence of ProQ's structural elements and specific residues on mRNA binding.
• To assess the impact of small regulatory RNAs (sRNAs) on ProQ-mRNA association.

Main Methods:

• Single-molecule tracking in live bacteria.
• Analysis of ProQ interactions during different growth phases (exponential, stationary) and under osmotic stress.
• Site-directed mutagenesis to probe the role of specific ProQ residues (e.g., Y70) and domains.

Main Results:

• ProQ predominantly binds to mRNAs across various bacterial growth conditions and stress responses.
• All structural domains of ProQ (N-terminal, linker, C-terminal) contribute to mRNA binding.
• Residue Y70 is critical for global mRNA binding, while other N-terminal residues show varied effects, suggesting differential mRNA binding specificities.
• Expressed sRNAs have minimal impact on the proportion of mRNA-bound ProQ, likely due to high intracellular concentrations of unbound ProQ.

Conclusions:

• ProQ's interaction with mRNAs is widespread and influenced by its structural integrity and specific amino acid residues.
• The binding affinity of ProQ to different mRNAs may vary, mediated by distinct ProQ residues.
• The abundance of free ProQ in the cell likely limits the influence of sRNAs on ProQ-mRNA complex formation.