8Z4D

Structure of the S-ring region of the Vibrio flagellar MS-ring protein FliF with 34-fold symmetry applied

Summary for 8Z4D

• Entry DOI: 10.2210/pdb8z4d/pdb
• EMDB information: 39761
• Descriptor: Flagellar M-ring protein,Flagellar motor switch protein FliG (1 entity in total)
• Functional Keywords: complex, rotor, motor protein
• Biological source: Vibrio alginolyticus; More
• Total number of polymer chains: 34
• Total formula weight: 3550172.15

Authors

Takekawa, N.,Nishikino, T.,Kishikawa, J.,Hirose, M.,Kato, T.,Imada, K.,Homma, M. (deposition date: 2024-04-17, release date: 2024-09-04, Last modification date: 2025-07-02)

Primary citation

Takekawa, N.,Nishikino, T.,Kishikawa, J.I.,Hirose, M.,Kinoshita, M.,Kojima, S.,Minamino, T.,Uchihashi, T.,Kato, T.,Imada, K.,Homma, M.
Structural analysis of S-ring composed of FliFG fusion proteins in marine Vibrio polar flagellar motor.
Mbio, 15:e0126124-e0126124, 2024

PubMed Abstract: The marine bacterium possesses a polar flagellum driven by a sodium ion flow. The main components of the flagellar motor are the stator and rotor. The C-ring and MS-ring, which are composed of FliG and FliF, respectively, are parts of the rotor. Here, we purified an MS-ring composed of FliF-FliG fusion proteins and solved the near-atomic resolution structure of the S-ring-the upper part of the MS-ring-using cryo-electron microscopy. This is the first report of an S-ring structure from , whereas, previously, only those from have been reported. The S-ring structure reveals novel features compared with that of , such as tilt angle differences of the RBM3 domain and the β-collar region, which contribute to the vertical arrangement of the upper part of the β-collar region despite the diversity in the RBM3 domain angles. Additionally, there is a decrease of the inter-subunit interaction between RBM3 domains, which influences the efficiency of the MS-ring formation in different bacterial species. Furthermore, although the inner-surface electrostatic properties of and S-rings are altered, the residues potentially interacting with other flagellar components, such as FliE and FlgB, are well structurally conserved in the S-ring. These comparisons clarified the conserved and non-conserved structural features of the MS-ring across different species.IMPORTANCEUnderstanding the structure and function of the flagellar motor in bacterial species is essential for uncovering the mechanisms underlying bacterial motility and pathogenesis. Our study revealed the structure of the S-ring, a part of its polar flagellar motor, and highlighted its unique features compared with the well-studied S-ring. The observed differences in the inter-subunit interactions and in the tilt angles between the and S-rings highlighted the species-specific variations and the mechanism for the optimization of MS-ring formation in the flagellar assembly. By concentrating on the region where the S-ring and the rod proteins interact, we uncovered conserved residues essential for the interaction. Our research contributes to the advancement of bacterial flagellar biology.

PubMed: 39240115
DOI: 10.1128/mbio.01261-24

Experimental method

ELECTRON MICROSCOPY (3.33 Å)