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Publication Abstract from PubMed

Bacterial chemotaxis requires bidirectional flagellar rotation at different rates. Rotation is driven by a flagellar motor, which is a supercomplex containing multiple rings. Architectural uncertainty regarding the cytoplasmic C-ring, or 'switch', limits our understanding of how the motor transmits torque and direction to the flagellar rod. Here we report cryogenic electron microscopy structures for Salmonella enterica serovar typhimurium inner membrane MS-ring and C-ring in a counterclockwise pose (4.0 A) and isolated C-ring in a clockwise pose alone (4.6 A) and bound to a regulator (5.9 A). Conformational differences between rotational poses include a 180 degrees shift in FliF/FliG domains that rotates the outward-facing MotA/B binding site to inward facing. The regulator has specificity for the clockwise pose by bridging elements unique to this conformation. We used these structures to propose how the switch reverses rotation and transmits torque to the flagellum, which advances the understanding of bacterial chemotaxis and bidirectional motor rotation.

CryoEM structures reveal how the bacterial flagellum rotates and switches direction.,Singh PK, Sharma P, Afanzar O, Goldfarb MH, Maklashina E, Eisenbach M, Cecchini G, Iverson TM Nat Microbiol. 2024 May;9(5):1271-1281. doi: 10.1038/s41564-024-01674-1. Epub , 2024 Apr 17. PMID:38632342^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.