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Mechanism and kinetics of a sodium-driven bacterial flagellar motor

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Original languageEnglish
Pages (from-to)E2544-E2551
Number of pages8
JournalProceedings of the National Academy of Sciences
Issue number28
Publication statusPublished - 9 Jul 2013


The bacterial flagellar motor is a large rotary molecular machine that propels swimming bacteria, powered by a transmembrane electrochemical potential difference. It consists of an similar to 50-nm rotor and up to similar to 10 independent stators anchored to the cell wall. We measured torque-speed relationships of single-stator motors under 25 different combinations of electrical and chemical potential. All 25 torque-speed curves had the same concave-down shape as fully energized wild-type motors, and each stator passes at least 37 +/- 2 ions per revolution. We used the results to explore the 25-dimensional parameter space of generalized kinetic models for the motor mechanism, finding 830 parameter sets consistent with the data. Analysis of these sets showed that the motor mechanism has a "powerstroke" in either ion binding or transit; ion transit is channel-like rather than carrier-like; and the rate-limiting step in the motor cycle is ion binding at low concentration, ion transit, or release at high concentration.

    Research areas

  • ion-motive force, multidimensional modeling, sodium-motive force, molecular motor, single-molecule, torque-speed relationship, escherichia-coli, rotary motor, na+-driven, zero load, proton translocation, generating units, myosin-v, rotation, model

ID: 10120217