Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>

ABSTRACT Flagellin (Hag) is one of the most abundant proteins in Bacillus subtilis. Here we show that each flagellar filament is assembled from ∼12,000 Hag monomers and that there is a cytoplasmic pool of Hag that is restricted to 5% of the total. Hag is thought to be restricted at the level of tran...

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Autores principales:	R. T. Oshiro, S. Rajendren, H. A. Hundley, D. B. Kearns
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	FtsZ flagella fliC homeostasis minicell motility Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/fc286c92f171417998e246869354c0dc
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spelling	oai:doaj.org-article:fc286c92f171417998e246869354c0dc2021-11-15T15:55:25ZRobust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>10.1128/mBio.00533-192150-7511https://doaj.org/article/fc286c92f171417998e246869354c0dc2019-06-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00533-19https://doaj.org/toc/2150-7511ABSTRACT Flagellin (Hag) is one of the most abundant proteins in Bacillus subtilis. Here we show that each flagellar filament is assembled from ∼12,000 Hag monomers and that there is a cytoplasmic pool of Hag that is restricted to 5% of the total. Hag is thought to be restricted at the level of translation by a partner-switching mechanism involving FliW and the homodimeric RNA-binding protein CsrA (CsrAdimer). We further show that the mechanism of translation inhibition is hypersensitive due to a 1:1 ratio of Hag to FliW, a 1:1 inhibitory ratio of FliW to CsrAdimer, and a nearly 1:1 ratio of CsrAdimer to hag transcripts. Equimolarity of all components couples single-molecule detection of Hag export to compensatory translation and causes cytoplasmic Hag concentrations to oscillate around the level of FliW. We found that stoichiometry is ensured by genetic architecture, translational coupling, and the ability of CsrAdimer to restrict hag transcript accumulation. We further show that homeostasis prevents Hag hyperaccumulation that would otherwise cause severe defects in intracellular architecture, perhaps due to increased molecular crowding. We note that FliW-CsrA-mediated structural homeostasis has similarities to that seen with some toxin-antitoxin systems. IMPORTANCE The intracellular concentration of flagellar filament protein Hag is restricted by the Hag-FliW-CsrA system in B. subtilis. Here we show that the Hag-FliW-CsrAdimer system functions at nearly 1:1:1 stoichiometry and that the system is both robust with respect to perturbation and hypersensitive to the Hag intracellular concentration. Moreover, restriction of cytoplasmic Hag levels is important for maintaining proper intracellular architecture, as artificial Hag hyperaccumulation led to generalized spatial defects and a high frequency of minicell production. The Hag-FliW-CsrA system is conserved in the deeper branches of bacterial phylogeny, and we note that the Hag-FliW-CsrA “homeostasis module” resembles a toxin-antitoxin system where, by analogy, CsrA is the “toxin,” FliW is the “antitoxin,” and Hag is the target.R. T. OshiroS. RajendrenH. A. HundleyD. B. KearnsAmerican Society for MicrobiologyarticleFtsZflagellafliChomeostasisminicellmotilityMicrobiologyQR1-502ENmBio, Vol 10, Iss 3 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	FtsZ flagella fliC homeostasis minicell motility Microbiology QR1-502
spellingShingle	FtsZ flagella fliC homeostasis minicell motility Microbiology QR1-502 R. T. Oshiro S. Rajendren H. A. Hundley D. B. Kearns Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
description	ABSTRACT Flagellin (Hag) is one of the most abundant proteins in Bacillus subtilis. Here we show that each flagellar filament is assembled from ∼12,000 Hag monomers and that there is a cytoplasmic pool of Hag that is restricted to 5% of the total. Hag is thought to be restricted at the level of translation by a partner-switching mechanism involving FliW and the homodimeric RNA-binding protein CsrA (CsrAdimer). We further show that the mechanism of translation inhibition is hypersensitive due to a 1:1 ratio of Hag to FliW, a 1:1 inhibitory ratio of FliW to CsrAdimer, and a nearly 1:1 ratio of CsrAdimer to hag transcripts. Equimolarity of all components couples single-molecule detection of Hag export to compensatory translation and causes cytoplasmic Hag concentrations to oscillate around the level of FliW. We found that stoichiometry is ensured by genetic architecture, translational coupling, and the ability of CsrAdimer to restrict hag transcript accumulation. We further show that homeostasis prevents Hag hyperaccumulation that would otherwise cause severe defects in intracellular architecture, perhaps due to increased molecular crowding. We note that FliW-CsrA-mediated structural homeostasis has similarities to that seen with some toxin-antitoxin systems. IMPORTANCE The intracellular concentration of flagellar filament protein Hag is restricted by the Hag-FliW-CsrA system in B. subtilis. Here we show that the Hag-FliW-CsrAdimer system functions at nearly 1:1:1 stoichiometry and that the system is both robust with respect to perturbation and hypersensitive to the Hag intracellular concentration. Moreover, restriction of cytoplasmic Hag levels is important for maintaining proper intracellular architecture, as artificial Hag hyperaccumulation led to generalized spatial defects and a high frequency of minicell production. The Hag-FliW-CsrA system is conserved in the deeper branches of bacterial phylogeny, and we note that the Hag-FliW-CsrA “homeostasis module” resembles a toxin-antitoxin system where, by analogy, CsrA is the “toxin,” FliW is the “antitoxin,” and Hag is the target.
format	article
author	R. T. Oshiro S. Rajendren H. A. Hundley D. B. Kearns
author_facet	R. T. Oshiro S. Rajendren H. A. Hundley D. B. Kearns
author_sort	R. T. Oshiro
title	Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
title_short	Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
title_full	Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
title_fullStr	Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
title_full_unstemmed	Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>
title_sort	robust stoichiometry of fliw-csra governs flagellin homeostasis and cytoplasmic organization in <named-content content-type="genus-species">bacillus subtilis</named-content>
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/fc286c92f171417998e246869354c0dc
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Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in <named-content content-type="genus-species">Bacillus subtilis</named-content>

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