Effect of Intracellular pH on the Torque-Speed Relationship of Bacterial Proton-Driven Flagellar Motor

Shuichi Nakamura, Nobunori Kami-ike, Jun ichi P. Yokota, Seishi Kudo, Tohru Minamino, Keiichi Namba

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

Bacterial flagella responsible for motility are driven by rotary motors powered by the electrochemical potential difference of specific ions across the cytoplasmic membrane. The stator of proton-driven flagellar motor converts proton influx into mechanical work. However, the energy conversion mechanism remains unclear. Here, we show that the motor is sensitive to intracellular proton concentration for high-speed rotation at low load, which was considerably impaired by lowering intracellular pH, while zero-speed torque was not affected. The change in extracellular pH did not show any effect. These results suggest that a high intracellular proton concentration decreases the rate of proton translocation and therefore that of the mechanochemical reaction cycle of the motor but not the actual torque generation step within the cycle by the stator-rotor interactions.

Original languageEnglish
Pages (from-to)332-338
Number of pages7
JournalJournal of Molecular Biology
Volume386
Issue number2
DOIs
Publication statusPublished - 2009 Feb 20

Keywords

  • bacterial flagellar motor
  • intracellular pH
  • proton translocation
  • stator complex
  • torque generation

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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