Interaction between Na+ ion and carboxylates of the PomA-PomB stator unit studied by ATR-FTIR spectroscopy

Yuki Sudo, Yuya Kitade, Yuji Furutani, Masaru Kojima, Seiji Kojima, Michio Homma, Hideki Kandori

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


Bacterial flagellar motors are molecular machines powered by the electrochemical potential gradient of specific ions across the membrane. The PomA-PomB stator complex of Vibrio alginolyticus couples Na+ influx to torque generation in this supramolecular motor, but little is known about how Na+ associates with the PomA-PomB complex in the energy conversion process. Here, by means of attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy, we directly observed binding of Na+ to carboxylates in the PomA-PomB complex, including the functionally essential residue Asp24. The Na+ affinity of Asp24 is estimated to be ∼85 mM, close to the apparent Km value from the swimming motility of the cells (78 mM). At least two other carboxylates are shown to be capable of interacting with Na+, but with somewhat lower affinities. We conclude that Asp24 and at least two other carboxylates constitute Na+ interaction sites in the PomA-PomB complex. This work reveals features of the Na+ pathway in the PomA-PomB Na+ channel by using vibrational spectroscopy.

Original languageEnglish
Pages (from-to)11699-11705
Number of pages7
Issue number49
Publication statusPublished - Dec 15 2009
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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