Rotational fluctuation of the sodium-driven flagellar motor of Vibrio alginolyticus induced by binding of inhibitors

J Mol Biol. 1996 Jun 21;259(4):687-95. doi: 10.1006/jmbi.1996.0350.


Rotation of the Na(+)-driven flagellar motor of Vibrio alginolyticus was investigated under the influence of inhibitors specific to the motor, amiloride and phenamil. The rotation rate of a single flagellum on a cell stuck to a glass slide was examined using laser dark-field microscopy. In the presence of 50 mM NaCl, the average rotation rate (omega) was about 600 r.p.s. with a standard deviation (sigma omega) of 9% of omega. When omega was decreased to about 200 r.p.s. by the presence of 1.5 mM amiloride, sigma omega increased to 15% of omega. On the other hand, when omega was decreased to about 200 r.p.s. by the addition of 0.6 microM phenamil, a large increase in sigma omega up to 50% of omega, was observed. Similarly large fluctuations were observed at other concentrations of phenamil. These observations suggest that dissociation of phenamil from the motor was much slower than that of amiloride. A very low concentration of phenamil caused a transient but substantial reduction in rotation rate. This might suggest that binding of only a single molecule of phenamil strongly inhibits the torque generation in the flagellar motor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / analogs & derivatives
  • Amiloride / pharmacology
  • Cell Division / drug effects
  • Computer Simulation
  • Flagella / metabolism
  • Flagella / physiology*
  • Microscopy
  • Models, Biological
  • Molecular Structure
  • Movement / drug effects
  • Protein Binding
  • Sodium / antagonists & inhibitors
  • Sodium / metabolism*
  • Sodium Channel Blockers
  • Sodium Channels / drug effects
  • Vibrio / growth & development
  • Vibrio / metabolism
  • Vibrio / physiology*


  • Sodium Channel Blockers
  • Sodium Channels
  • phenylamil
  • Amiloride
  • Sodium