Effect of the MotB(D33N) mutation on stator assembly and rotation of the proton-driven bacterial flagellar motor

Shuichi Nakamura, Tohru Minamino, Nobunori Kami-Ike, Seishi Kudo, Keiichi Namba

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The bacterial flagellar motor generates torque by converting the energy of proton translocation through the transmembrane proton channel of the stator complex formed by MotA and MotB. The MotA/B complex is thought to be anchored to the peptidoglycan (PG) layer through the PG-binding domain of MotB to act as the stator. The stator units dynamically associate with and dissociate from the motor during flagellar motor rotation, and an electrostatic interaction between MotA and a rotor protein FliG is required for efficient stator assembly. However, the association and dissociation mechanism of the stator units still remains unclear. In this study, we analyzed the speed fluctuation of the flagellar motor of Salmonella enterica wild-type cells carrying a plasmid encoding a nonfunctional stator complex, MotA/ B(D33N), which lost the proton conductivity. The wildtype motor rotated stably but the motor speed fluctuated considerably when the expression level of MotA/B(D33N) was relatively high compared to MotA/B. Rapid accelerations and decelerations were frequently observed. A quantitative analysis of the speed fluctuation and a model simulation suggested that the MotA/B(D33N) stator retains the ability to associate with the motor at a low affinity but dissociates more rapidly than the MotA/B stator. We propose that the stator dissociation process depends on proton translocation through the proton channel.

Original languageEnglish
Pages (from-to)35-41
Number of pages7
JournalBiophysics (Japan)
Publication statusPublished - 2014


  • Proton channel
  • Salmonella
  • Speed fluctuation
  • Stator
  • Torque generation

ASJC Scopus subject areas

  • Biophysics


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