Structural insight into the rotational switching mechanism of the bacterial flagellar motor.

The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid switching between the CW and CCW directions. Switching is achieved by a conformational change in FliG induced by the binding of a chemotaxi...

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Autores principales:	Tohru Minamino, Katsumi Imada, Miki Kinoshita, Shuichi Nakamura, Yusuke V Morimoto, Keiichi Namba
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2011
Materias:	Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/e640cdb0e4124505870b1a3da7b50ca3
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spelling	oai:doaj.org-article:e640cdb0e4124505870b1a3da7b50ca32021-11-18T05:36:12ZStructural insight into the rotational switching mechanism of the bacterial flagellar motor.1544-91731545-788510.1371/journal.pbio.1000616https://doaj.org/article/e640cdb0e4124505870b1a3da7b50ca32011-05-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21572987/?tool=EBIhttps://doaj.org/toc/1544-9173https://doaj.org/toc/1545-7885The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid switching between the CW and CCW directions. Switching is achieved by a conformational change in FliG induced by the binding of a chemotaxis signaling protein, phospho-CheY, to FliM and FliN. FliG consists of three domains, FliG(N), FliG(M), and FliG(C), and forms a ring on the cytoplasmic face of the MS ring of the flagellar basal body. Crystal structures have been reported for the FliG(MC) domains of Thermotoga maritima, which consist of the FliG(M) and FliG(C) domains and a helix E that connects these two domains, and full-length FliG of Aquifex aeolicus. However, the basis for the switching mechanism is based only on previously obtained genetic data and is hence rather indirect. We characterized a CW-biased mutant (fliG(ΔPAA)) of Salmonella enterica by direct observation of rotation of a single motor at high temporal and spatial resolution. We also determined the crystal structure of the FliG(MC) domains of an equivalent deletion mutant variant of T. maritima (fliG(ΔPEV)). The FliG(ΔPAA) motor produced torque at wild-type levels under a wide range of external load conditions. The wild-type motors rotated exclusively in the CCW direction under our experimental conditions, whereas the mutant motors rotated only in the CW direction. This result suggests that wild-type FliG is more stable in the CCW state than in the CW state, whereas FliG(ΔPAA) is more stable in the CW state than in the CCW state. The structure of the TM-FliG(MC)(ΔPEV) revealed that extremely CW-biased rotation was caused by a conformational change in helix E. Although the arrangement of FliG(C) relative to FliG(M) in a single molecule was different among the three crystals, a conserved FliG(M)-FliG(C) unit was observed in all three of them. We suggest that the conserved FliG(M)-FliG(C) unit is the basic functional element in the rotor ring and that the PAA deletion induces a conformational change in a hinge-loop between FliG(M) and helix E to achieve the CW state of the FliG ring. We also propose a novel model for the arrangement of FliG subunits within the motor. The model is in agreement with the previous mutational and cross-linking experiments and explains the cooperative switching mechanism of the flagellar motor.Tohru MinaminoKatsumi ImadaMiki KinoshitaShuichi NakamuraYusuke V MorimotoKeiichi NambaPublic Library of Science (PLoS)articleBiology (General)QH301-705.5ENPLoS Biology, Vol 9, Iss 5, p e1000616 (2011)
institution	DOAJ
collection	DOAJ
language	EN
topic	Biology (General) QH301-705.5
spellingShingle	Biology (General) QH301-705.5 Tohru Minamino Katsumi Imada Miki Kinoshita Shuichi Nakamura Yusuke V Morimoto Keiichi Namba Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
description	The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid switching between the CW and CCW directions. Switching is achieved by a conformational change in FliG induced by the binding of a chemotaxis signaling protein, phospho-CheY, to FliM and FliN. FliG consists of three domains, FliG(N), FliG(M), and FliG(C), and forms a ring on the cytoplasmic face of the MS ring of the flagellar basal body. Crystal structures have been reported for the FliG(MC) domains of Thermotoga maritima, which consist of the FliG(M) and FliG(C) domains and a helix E that connects these two domains, and full-length FliG of Aquifex aeolicus. However, the basis for the switching mechanism is based only on previously obtained genetic data and is hence rather indirect. We characterized a CW-biased mutant (fliG(ΔPAA)) of Salmonella enterica by direct observation of rotation of a single motor at high temporal and spatial resolution. We also determined the crystal structure of the FliG(MC) domains of an equivalent deletion mutant variant of T. maritima (fliG(ΔPEV)). The FliG(ΔPAA) motor produced torque at wild-type levels under a wide range of external load conditions. The wild-type motors rotated exclusively in the CCW direction under our experimental conditions, whereas the mutant motors rotated only in the CW direction. This result suggests that wild-type FliG is more stable in the CCW state than in the CW state, whereas FliG(ΔPAA) is more stable in the CW state than in the CCW state. The structure of the TM-FliG(MC)(ΔPEV) revealed that extremely CW-biased rotation was caused by a conformational change in helix E. Although the arrangement of FliG(C) relative to FliG(M) in a single molecule was different among the three crystals, a conserved FliG(M)-FliG(C) unit was observed in all three of them. We suggest that the conserved FliG(M)-FliG(C) unit is the basic functional element in the rotor ring and that the PAA deletion induces a conformational change in a hinge-loop between FliG(M) and helix E to achieve the CW state of the FliG ring. We also propose a novel model for the arrangement of FliG subunits within the motor. The model is in agreement with the previous mutational and cross-linking experiments and explains the cooperative switching mechanism of the flagellar motor.
format	article
author	Tohru Minamino Katsumi Imada Miki Kinoshita Shuichi Nakamura Yusuke V Morimoto Keiichi Namba
author_facet	Tohru Minamino Katsumi Imada Miki Kinoshita Shuichi Nakamura Yusuke V Morimoto Keiichi Namba
author_sort	Tohru Minamino
title	Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
title_short	Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
title_full	Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
title_fullStr	Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
title_full_unstemmed	Structural insight into the rotational switching mechanism of the bacterial flagellar motor.
title_sort	structural insight into the rotational switching mechanism of the bacterial flagellar motor.
publisher	Public Library of Science (PLoS)
publishDate	2011
url	https://doaj.org/article/e640cdb0e4124505870b1a3da7b50ca3
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_version_	1718424947291848704

Structural insight into the rotational switching mechanism of the bacterial flagellar motor.

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