title: Torque-speed relationship of the Na+-driven flagellar motor of Vibrio alginolyticus.
abstract: The torque-speed relationship of the Na(+)-driven flagellar motor of Vibrio alginolyticus was investigated. The rotation rate of the motor was measured by following the position of a bead, attached to a flagellar filament, using optical nanometry. In the presence of 50mM NaCl, the generated torque was relatively constant ( approximately 3800pNnm) at lower speeds (speeds up to approximately 300Hz) and then decreased steeply, similar to the H(+)-driven flagellar motor of Escherichia coli. When the external NaCl concentration was varied, the generated torque of the flagellar motor was changed over a wide range of speeds. This result could be reproduced using a simple kinetic model, which takes into consideration the association and dissociation of Na(+) onto the motor. These results imply that for a complete understanding of the mechanism of flagellar rotation it is essential to consider both the electrochemical gradient and the absolute concentration of the coupling ion.
authors.affiliation: Department of Biophysical Engineering, Osaka University, 1-3, Machikaneyama, Toyonaka, 560-8531, Osaka, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Sowa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hotta
authors.forename: Michio
authors.initials: M
authors.lastname: Homma
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishijima
mesh_terms: D003470:Culture Media; D005407:Flagella / Q000502:physiology*; D012964:Sodium / Q000502:physiology*; D014733:Vibrio / Q000502:physiology*
chemical_list: D003470:Culture Media; D012964:Sodium