A multifunctional small RNA binding protein for sensing and signaling cell envelope precursor availability in...

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacterial cell envelope biosynthesis is initiated by glucosamine-6-phosphate (GlcN6P) synthesis via GlmS.
• Maintaining GlcN6P homeostasis is crucial for sustained bacterial growth.
• Escherichia coli employs a post-transcriptional regulatory network involving RapZ, GlmY, and GlmZ sRNAs.

Purpose of the Study:

• To identify the metabolite sensor in the GlcN6P homeostasis regulatory network.
• To elucidate the mechanism by which RapZ controls GlmY and GlmZ sRNAs.
• To understand the interplay between RapZ, sRNAs, a two-component system, and RNase E.

Main Methods:

• Metabolite sensing assays to identify RapZ as the GlcN6P sensor.
• RNA-binding studies to characterize RapZ-GlmZ and RapZ-GlmY interactions.
• Two-component system (TCS) phosphorylation assays involving QseE/QseF.
• Gene expression analysis of glmY and glmS.

Main Results:

• RapZ directly senses GlcN6P, acting as the primary metabolite sensor.
• GlcN6P-free RapZ activates the QseE/QseF TCS, leading to GlmY upregulation.
• GlmY sequesters RapZ, preventing GlmZ degradation and promoting glmS translation, creating a feedback loop.

Conclusions:

• RapZ integrates metabolic signals with RNA-based regulation to maintain GlcN6P homeostasis.
• The regulatory network involving RapZ, GlmY, GlmZ, QseE/QseF, and RNase E provides robust control over cell envelope synthesis.
• This study reveals a sophisticated mechanism for bacterial metabolite homeostasis and adaptation.