Mechanism and kinetics of a sodium-driven bacterial flagellar motor

Journal article

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 ∼50-nm rotor and up 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.

Authors: Lo, C; Sowa, Y; Pilizota, T; Berry, R; Lo, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: National Academy of Sciences
• Journal: Proceedings of the National Academy of Sciences of the United States of America
• Volume: 110
• Issue: 28
• Pages: E2544-E2551
• Publication date: 2013-07-01
• DOI: 10.1073/pnas.1301664110
• EISSN: 1091-6490
• ISSN: 0027-8424
• Language: English
• Keywords: ion-motive force; sodium; bacterial physiological phenomena; kinetics; flagella; multidimensional modeling; sodium-motive force; single-molecule; molecular motor