A multifunctional small RNA binding protein for sensing and signaling cell envelope precursor availability in bacteria
Authors:Muna A. Khan1 and Boris Görke1
doi: 10.15698/mic2020.05.717
Volume 7, pp. 139 to 142, published 15/04/2020.
1 Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, University of Vienna, Vienna Biocenter (VBC), 1030 Vienna, Austria.
Keywords:
RNA binding protein, metabolite sensing, small regulatory RNA, two-component system, cell envelope precursor, Escherichia coli
Corresponding Author(s):
Conflict of interest statement:
The authors declare that they have no conflict of interest.
Please cite this article as:
Muna A. Khan and Boris Görke (2020). A multifunctional small RNA binding protein for sensing and signaling cell envelope precursor availability in bacteria. Microbial Cell 7(5): 139-142. doi: 10.15698/mic2020.05.717
© 2020 Khan and Görke. This is an open-access article released under the terms of the Creative Commons At-tribution (CC BY) license, which allows the unrestricted use, distribution, and reproduction in any medium, pro-vided the original author and source are acknowledged.
Abstract:
Synthesis of glucosamine-6-phosphate (GlcN6P) by the enzyme GlmS initiates bacterial cell envelope biosynthesis. To ensure ongoing synthesis, GlcN6P homeostasis is required. Escherichia coli achieves this through a post-transcriptional control mechanism comprising the RNA-binding protein RapZ and small RNAs (sRNAs) GlmY and GlmZ. GlmZ stimulates glmS translation by base-pairing. When GlcN6P is abundant, GlmZ is cleaved and inactivated by endoribonuclease RNase E. Cleavage depends on RapZ, which binds GlmZ and recruits RNase E. Decreasing GlcN6P concentrations provoke up-regulation of the decoy sRNA GlmY which sequesters RapZ, thereby suppressing GlmZ decay. In our current study we identify RapZ as the GlcN6P sensor. GlcN6P-free RapZ interacts with and stimulates phosphorylation of the two-component system (TCS) QseE/QseF triggering glmY expression. Thereby generated GlmY sequesters RapZ into stable complexes, allowing for glmS expression. Sequestration by GlmY also disables RapZ to stimulate QseE/QseF, providing a negative feed-back loop limiting the response. When GlcN6P is replenished, GlmY is released from RapZ and rapidly degraded. Our work has revealed a complex regulatory scenario, in which an RNA binding protein senses a metabolite and communicates with two sRNAs, a TCS and ribonuclease RNase E to achieve metabolite homeostasis.