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Updated: Jun 24, 2026

Biophysical Characterization of Flagellar Motor Functions
Published on: January 18, 2017
A molecular mechanism of bacterial flagellar motor switching
Collin M Dyer1, Armand S Vartanian, Hongjun Zhou
1Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.
Abstract:
The high-resolution structures of nearly all the proteins that comprise the bacterial flagellar motor switch complex have been solved; yet a clear picture of the switching mechanism has not emerged. Here, we used NMR to characterize the interaction modes and solution properties of a number of these proteins, including several soluble fragments of the flagellar motor proteins FliM and FliG, and the response-regulator CheY. We find that activated CheY, the switch signal, binds to a previously unidentified region of FliM, adjacent to the FliM-FliM interface. We also find that activated CheY and FliG bind with mutual exclusivity to this site on FliM, because their respective binding surfaces partially overlap. These data support a model of CheY-driven motor switching wherein the binding of activated CheY to FliM displaces the carboxy-terminal domain of FliG (FliGC) from FliM, modulating the FliGC-MotA interaction, and causing the motor to switch rotational sense as required for chemotaxis.
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