Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex

ABSTRACT The flagellar motor can spin in both counterclockwise (CCW) and clockwise (CW) directions. The flagellar motor consists of a rotor and multiple stator units, which act as a proton channel. The rotor is composed of the transmembrane MS ring made of FliF and the cytoplasmic C ring consisting...

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Autores principales:	Tomofumi Sakai, Tomoko Miyata, Naoya Terahara, Koichiro Mori, Yumi Inoue, Yusuke V. Morimoto, Takayuki Kato, Keiichi Namba, Tohru Minamino
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	chemotaxis flagellar motility flagellar structure torque generation Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3e2fbf7f70ee4414af87e6ae05069a04
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spelling	oai:doaj.org-article:3e2fbf7f70ee4414af87e6ae05069a042021-11-15T15:55:25ZNovel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex10.1128/mBio.00079-192150-7511https://doaj.org/article/3e2fbf7f70ee4414af87e6ae05069a042019-04-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00079-19https://doaj.org/toc/2150-7511ABSTRACT The flagellar motor can spin in both counterclockwise (CCW) and clockwise (CW) directions. The flagellar motor consists of a rotor and multiple stator units, which act as a proton channel. The rotor is composed of the transmembrane MS ring made of FliF and the cytoplasmic C ring consisting of FliG, FliM, and FliN. The C ring is directly involved in rotation and directional switching. The Salmonella FliF-FliG deletion fusion motor missing 56 residues from the C terminus of FliF and 94 residues from the N terminus of FliG keeps a domain responsible for the interaction with the stator intact, but its motor function is reduced significantly. Here, we report the structure and function of the FliF-FliG deletion fusion motor. The FliF-FliG deletion fusion not only resulted in a strong CW switch bias but also affected rotor-stator interactions coupled with proton translocation through the proton channel of the stator unit. The energy coupling efficiency of the deletion fusion motor was the same as that of the wild-type motor. Extragenic suppressor mutations in FliG, FliM, or FliN not only relieved the strong CW switch bias but also increased the motor speed at low load. The FliF-FliG deletion fusion made intersubunit interactions between C ring proteins tighter compared to the wild-type motor, whereas the suppressor mutations affect such tighter intersubunit interactions. We propose that a change of intersubunit interactions between the C ring proteins may be required for high-speed motor rotation as well as direction switching. IMPORTANCE The bacterial flagellar motor is a bidirectional rotary motor for motility and chemotaxis, which often plays an important role in infection. The motor is a large transmembrane protein complex composed of a rotor and multiple stator units, which also act as a proton channel. Motor torque is generated through their cyclic association and dissociation coupled with proton translocation through the proton channel. A large cytoplasmic ring of the motor, called C ring, is responsible for rotation and switching by interacting with the stator, but the mechanism remains unknown. By analyzing the structure and function of the wild-type motor and a mutant motor missing part of the C ring connecting itself with the transmembrane rotor ring while keeping a stator-interacting domain for bidirectional torque generation intact, we found interesting clues to the change in the C ring conformation for the switching and rotation involving loose and tight intersubunit interactions.Tomofumi SakaiTomoko MiyataNaoya TeraharaKoichiro MoriYumi InoueYusuke V. MorimotoTakayuki KatoKeiichi NambaTohru MinaminoAmerican Society for Microbiologyarticlechemotaxisflagellar motilityflagellar structuretorque generationMicrobiologyQR1-502ENmBio, Vol 10, Iss 2 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	chemotaxis flagellar motility flagellar structure torque generation Microbiology QR1-502
spellingShingle	chemotaxis flagellar motility flagellar structure torque generation Microbiology QR1-502 Tomofumi Sakai Tomoko Miyata Naoya Terahara Koichiro Mori Yumi Inoue Yusuke V. Morimoto Takayuki Kato Keiichi Namba Tohru Minamino Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
description	ABSTRACT The flagellar motor can spin in both counterclockwise (CCW) and clockwise (CW) directions. The flagellar motor consists of a rotor and multiple stator units, which act as a proton channel. The rotor is composed of the transmembrane MS ring made of FliF and the cytoplasmic C ring consisting of FliG, FliM, and FliN. The C ring is directly involved in rotation and directional switching. The Salmonella FliF-FliG deletion fusion motor missing 56 residues from the C terminus of FliF and 94 residues from the N terminus of FliG keeps a domain responsible for the interaction with the stator intact, but its motor function is reduced significantly. Here, we report the structure and function of the FliF-FliG deletion fusion motor. The FliF-FliG deletion fusion not only resulted in a strong CW switch bias but also affected rotor-stator interactions coupled with proton translocation through the proton channel of the stator unit. The energy coupling efficiency of the deletion fusion motor was the same as that of the wild-type motor. Extragenic suppressor mutations in FliG, FliM, or FliN not only relieved the strong CW switch bias but also increased the motor speed at low load. The FliF-FliG deletion fusion made intersubunit interactions between C ring proteins tighter compared to the wild-type motor, whereas the suppressor mutations affect such tighter intersubunit interactions. We propose that a change of intersubunit interactions between the C ring proteins may be required for high-speed motor rotation as well as direction switching. IMPORTANCE The bacterial flagellar motor is a bidirectional rotary motor for motility and chemotaxis, which often plays an important role in infection. The motor is a large transmembrane protein complex composed of a rotor and multiple stator units, which also act as a proton channel. Motor torque is generated through their cyclic association and dissociation coupled with proton translocation through the proton channel. A large cytoplasmic ring of the motor, called C ring, is responsible for rotation and switching by interacting with the stator, but the mechanism remains unknown. By analyzing the structure and function of the wild-type motor and a mutant motor missing part of the C ring connecting itself with the transmembrane rotor ring while keeping a stator-interacting domain for bidirectional torque generation intact, we found interesting clues to the change in the C ring conformation for the switching and rotation involving loose and tight intersubunit interactions.
format	article
author	Tomofumi Sakai Tomoko Miyata Naoya Terahara Koichiro Mori Yumi Inoue Yusuke V. Morimoto Takayuki Kato Keiichi Namba Tohru Minamino
author_facet	Tomofumi Sakai Tomoko Miyata Naoya Terahara Koichiro Mori Yumi Inoue Yusuke V. Morimoto Takayuki Kato Keiichi Namba Tohru Minamino
author_sort	Tomofumi Sakai
title	Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
title_short	Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
title_full	Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
title_fullStr	Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
title_full_unstemmed	Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
title_sort	novel insights into conformational rearrangements of the bacterial flagellar switch complex
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/3e2fbf7f70ee4414af87e6ae05069a04
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Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex

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