Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN

ABSTRACT Some proteins in biological complexes exchange with pools of free proteins while the complex is functioning. Evidence is emerging that protein exchange can be part of an adaptive mechanism. The bacterial flagellar motor is one of the most complex biological machines and is an ideal model sy...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Nicolas J. Delalez, Richard M. Berry, Judith P. Armitage
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2014
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/8b56e806756745b29fca346facbba8f6
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:8b56e806756745b29fca346facbba8f6
record_format	dspace
spelling	oai:doaj.org-article:8b56e806756745b29fca346facbba8f62021-11-15T15:47:22ZStoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN10.1128/mBio.01216-142150-7511https://doaj.org/article/8b56e806756745b29fca346facbba8f62014-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01216-14https://doaj.org/toc/2150-7511ABSTRACT Some proteins in biological complexes exchange with pools of free proteins while the complex is functioning. Evidence is emerging that protein exchange can be part of an adaptive mechanism. The bacterial flagellar motor is one of the most complex biological machines and is an ideal model system to study protein dynamics in large multimeric complexes. Recent studies showed that the copy number of FliM in the switch complex and the fraction of FliM that exchanges vary with the direction of flagellar rotation. Here, we investigated the stoichiometry and turnover of another switch complex component, FliN, labeled with the fluorescent protein CyPet, in Escherichia coli. Our results confirm that, in vivo, FliM and FliN form a complex with stoichiometry of 1:4 and function as a unit. We estimated that wild-type motors contained 120 ± 26 FliN molecules. Motors that rotated only clockwise (CW) or counterclockwise (CCW) contained 114 ± 17 and 144 ± 26 FliN molecules, respectively. The ratio of CCW-to-CW FliN copy numbers was 1.26, very close to that of 1.29 reported previously for FliM. We also measured the exchange of FliN molecules, which had a time scale and dependence upon rotation direction similar to those of FliM, consistent with an exchange of FliM-FliN as a unit. Our work confirms the highly dynamic nature of multimeric protein complexes and indicates that, under physiological conditions, these machines might not be the stable, complete structures suggested by averaged fixed methodologies but, rather, incomplete rings that can respond and adapt to changing environments. IMPORTANCE The flagellum is one of the most complex structures in a bacterial cell, with the core motor proteins conserved across species. Evidence is now emerging that turnover of some of these motor proteins depends on motor activity, suggesting that turnover is important for function. The switch complex transmits the chemosensory signal to the rotor, and we show, by using single-cell measurement, that both the copy number and the fraction of exchanging molecules vary with the rotational bias of the rotor. When the motor is locked in counterclockwise rotation, the copy number is similar to that determined by averaged, fixed methodologies, but when locked in a clockwise direction, the number is much lower, suggesting that that the switch complex ring is incomplete. Our results suggest that motor remodeling is an important component in tuning responses and adaptation at the motor.Nicolas J. DelalezRichard M. BerryJudith P. ArmitageAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 5, Iss 4 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Nicolas J. Delalez Richard M. Berry Judith P. Armitage Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
description	ABSTRACT Some proteins in biological complexes exchange with pools of free proteins while the complex is functioning. Evidence is emerging that protein exchange can be part of an adaptive mechanism. The bacterial flagellar motor is one of the most complex biological machines and is an ideal model system to study protein dynamics in large multimeric complexes. Recent studies showed that the copy number of FliM in the switch complex and the fraction of FliM that exchanges vary with the direction of flagellar rotation. Here, we investigated the stoichiometry and turnover of another switch complex component, FliN, labeled with the fluorescent protein CyPet, in Escherichia coli. Our results confirm that, in vivo, FliM and FliN form a complex with stoichiometry of 1:4 and function as a unit. We estimated that wild-type motors contained 120 ± 26 FliN molecules. Motors that rotated only clockwise (CW) or counterclockwise (CCW) contained 114 ± 17 and 144 ± 26 FliN molecules, respectively. The ratio of CCW-to-CW FliN copy numbers was 1.26, very close to that of 1.29 reported previously for FliM. We also measured the exchange of FliN molecules, which had a time scale and dependence upon rotation direction similar to those of FliM, consistent with an exchange of FliM-FliN as a unit. Our work confirms the highly dynamic nature of multimeric protein complexes and indicates that, under physiological conditions, these machines might not be the stable, complete structures suggested by averaged fixed methodologies but, rather, incomplete rings that can respond and adapt to changing environments. IMPORTANCE The flagellum is one of the most complex structures in a bacterial cell, with the core motor proteins conserved across species. Evidence is now emerging that turnover of some of these motor proteins depends on motor activity, suggesting that turnover is important for function. The switch complex transmits the chemosensory signal to the rotor, and we show, by using single-cell measurement, that both the copy number and the fraction of exchanging molecules vary with the rotational bias of the rotor. When the motor is locked in counterclockwise rotation, the copy number is similar to that determined by averaged, fixed methodologies, but when locked in a clockwise direction, the number is much lower, suggesting that that the switch complex ring is incomplete. Our results suggest that motor remodeling is an important component in tuning responses and adaptation at the motor.
format	article
author	Nicolas J. Delalez Richard M. Berry Judith P. Armitage
author_facet	Nicolas J. Delalez Richard M. Berry Judith P. Armitage
author_sort	Nicolas J. Delalez
title	Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
title_short	Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
title_full	Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
title_fullStr	Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
title_full_unstemmed	Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN
title_sort	stoichiometry and turnover of the bacterial flagellar switch protein flin
publisher	American Society for Microbiology
publishDate	2014
url	https://doaj.org/article/8b56e806756745b29fca346facbba8f6
work_keys_str_mv	AT nicolasjdelalez stoichiometryandturnoverofthebacterialflagellarswitchproteinflin AT richardmberry stoichiometryandturnoverofthebacterialflagellarswitchproteinflin AT judithparmitage stoichiometryandturnoverofthebacterialflagellarswitchproteinflin
_version_	1718427529756278784

Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN

Ejemplares similares