9RCD

Sheathed flagellar filament in Vibrio alginolyticus

This is a non-PDB format compatible entry.

Summary for 9RCD

• Entry DOI: 10.2210/pdb9rcd/pdb
• EMDB information: 53917
• Descriptor: Flagellin (1 entity in total)
• Functional Keywords: flaa, flagellin, filament, vibrio alginolyticus, structural protein
• Biological source: Vibrio alginolyticus
• Total number of polymer chains: 44
• Total formula weight: 1764977.68

Authors

Qin, K.,Einenkel, R.,Erhardt, M.,Bergeron, J.R.C. (deposition date: 2025-05-27, release date: 2026-04-15, Last modification date: 2026-05-06)

Primary citation

Qin, K.,Einenkel, R.,Zhao, W.,Kuhne, C.,Atherton, J.,Erhardt, M.,Bergeron, J.R.C.
The structure of the Vibrio alginolyticus flagellar filament suggests molecular mechanism for the rotation of sheathed flagella.
Nat Commun, 17:-, 2026

PubMed Abstract: In several pathogenic bacteria, including Vibrio species, the filament of the bacterial flagellum is encased by a membranous sheath, an extension of the bacterial outer membrane. It has been proposed that having sheathed flagella permit bacteria to evade an immune response against flagellar components, suggesting a role in virulence. However, the molecular details of the interaction between sheath and filament, and how it impacts filament rotation, remain largely uncharacterized. Here, we combine single-particle cryo-electron microscopy, cryo-electron tomography, and genetic analyses to resolve the molecular architecture and biogenesis of the sheathed flagellum in Vibrio alginolyticus. We show that the flagellar filament forms a canonical 11-stranded supercoil made of the flagellin FlaD2 and enveloped by a bilayered sheath. We report that the filament surface is highly electronegative, suggesting that electrostatic repulsion between filament and sheath may reduce friction and supports high-speed flagellar rotation. We also show that the filament cap protein FliD possesses a unique domain in sheathed flagella, that may coordinate sheath assembly with filament elongation. Collectively, this structural insight into the structure of the Vibrio alginolyticus flagellum suggests a molecular mechanism for the rotation of sheathed flagella.

PubMed: 42026045
DOI: 10.1038/s41467-026-71203-7

Experimental method

ELECTRON MICROSCOPY (3.6 Å)