Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries

Abstract The flagellar MS-ring is the initial template for flagellar assembly and houses the flagellar protein export complex. The MS-ring has three parts of different symmetries within the ring structure by assembly of FliF subunits in two different conformations with distinct arrangements of three...

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Main Authors: Miki Kinoshita, Fumiaki Makino, Tomoko Miyata, Katsumi Imada, Keiichi Namba, Tohru Minamino
Format: Article
Language:English
Published: Nature Portfolio 2025-01-01
Series:Communications Biology
Online Access:https://doi.org/10.1038/s42003-025-07485-2
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author Miki Kinoshita
Fumiaki Makino
Tomoko Miyata
Katsumi Imada
Keiichi Namba
Tohru Minamino
author_facet Miki Kinoshita
Fumiaki Makino
Tomoko Miyata
Katsumi Imada
Keiichi Namba
Tohru Minamino
author_sort Miki Kinoshita
collection DOAJ
description Abstract The flagellar MS-ring is the initial template for flagellar assembly and houses the flagellar protein export complex. The MS-ring has three parts of different symmetries within the ring structure by assembly of FliF subunits in two different conformations with distinct arrangements of three ring-building motifs, RBM1, RBM2, and RBM3. However, it remains unknown how these symmetries are generated. A combination of cryoEM structure and structure-based mutational analyses demonstrates that the well-conserved DQxGxxL motif in the RBM2-RBM3 hinge loop allows RBM2 to take two different orientations relative to RBM3. Of 34 FliF subunits of the MS-ring in the basal body, 23 RBM2 domains form an inner ring with a central pore that accommodates the flagellar protein export complex, and the remaining 11 RBM2 domains form 11 cog-like structures together with RBM1 domains just outside the inner RBM2-ring. We propose that a dimer of FliF with two different conformations initiates MS-ring assembly.
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spelling doaj-art-d148576f3ce543828e328995ea9f535f2025-01-19T12:35:39ZengNature PortfolioCommunications Biology2399-36422025-01-018111310.1038/s42003-025-07485-2Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetriesMiki Kinoshita0Fumiaki Makino1Tomoko Miyata2Katsumi Imada3Keiichi Namba4Tohru Minamino5Graduate School of Frontier Biosciences, Osaka UniversityGraduate School of Frontier Biosciences, Osaka UniversityGraduate School of Frontier Biosciences, Osaka UniversityDepartment of Macromolecular Science, Graduate School of Science, Osaka UniversityGraduate School of Frontier Biosciences, Osaka UniversityGraduate School of Frontier Biosciences, Osaka UniversityAbstract The flagellar MS-ring is the initial template for flagellar assembly and houses the flagellar protein export complex. The MS-ring has three parts of different symmetries within the ring structure by assembly of FliF subunits in two different conformations with distinct arrangements of three ring-building motifs, RBM1, RBM2, and RBM3. However, it remains unknown how these symmetries are generated. A combination of cryoEM structure and structure-based mutational analyses demonstrates that the well-conserved DQxGxxL motif in the RBM2-RBM3 hinge loop allows RBM2 to take two different orientations relative to RBM3. Of 34 FliF subunits of the MS-ring in the basal body, 23 RBM2 domains form an inner ring with a central pore that accommodates the flagellar protein export complex, and the remaining 11 RBM2 domains form 11 cog-like structures together with RBM1 domains just outside the inner RBM2-ring. We propose that a dimer of FliF with two different conformations initiates MS-ring assembly.https://doi.org/10.1038/s42003-025-07485-2
spellingShingle Miki Kinoshita
Fumiaki Makino
Tomoko Miyata
Katsumi Imada
Keiichi Namba
Tohru Minamino
Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
Communications Biology
title Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
title_full Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
title_fullStr Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
title_full_unstemmed Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
title_short Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries
title_sort structural basis for assembly and function of the salmonella flagellar ms ring with three different symmetries
url https://doi.org/10.1038/s42003-025-07485-2
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