- 著者
- Yuki Sudo Hiroyuki Terashima Rei Abe-Yoshizumi Seiji Kojima Michio Homma
- 出版者
- The Biophysical Society of Japan
- 雑誌
- BIOPHYSICS (ISSN:13492942)
- 巻号頁・発行日
- vol.5, pp.45-52, 2009 (Released:2009-06-12)
- 参考文献数
- 25
- 被引用文献数
- 18 22
Flagellar motor proteins, MotA/B and PomA/B, are essential for the motility of Escherichia coli and Vibrio alginolyticus, respectively. Those complexes work as a H+ and a Na+ channel, respectively and play important roles in torque generation as the stators of the flagellar motors. Although Asp32 of MotB and Asp24 of PomB are believed to function as ion binding site(s), the ion flux pathway from the periplasm to the cytoplasm is still unclear. Conserved residues, Ala39 of MotB and Cys31 of PomB, are located on the same sides as Asp32 of MotB and Asp24 of PomB, respectively, in a helical wheel diagram. In this study, a series of mutations were introduced into the Ala39 residue of MotB and the Cys31 residue of PomB. The motility of mutant cells were markedly decreased as the volume of the side chain increased. The loss of function due to the MotB(A39V) and PomB(L28A/C31A) mutations was suppressed by mutations of MotA(M206S) and PomA(L183F), respectively, and the increase in the volume caused by the MotB(A39V) mutation was close to the decrease in the volume caused by the MotA(M206S) mutation. These results demonstrate that Ala39 of MotB and Cys31 of PomB form part of the ion flux pathway and pore with Met206 of MotA and Leu183 of PomA in the MotA/B and PomA/B stator units, respectively.
- 著者
- Rei Abe Yoshizumi Shiori Kobayashi Mizuki Gohara Kokoro Hayashi Chojiro Kojima Seiji Kojima Yuki Sudo Yasuo Asami Michio Homma
- 出版者
- The Biophysical Society of Japan
- 雑誌
- BIOPHYSICS (ISSN:13492942)
- 巻号頁・発行日
- vol.9, pp.21-29, 2013 (Released:2013-02-05)
- 参考文献数
- 40
- 被引用文献数
- 2 2
Flagellar motors embedded in bacterial membranes are molecular machines powered by specific ion flows. Each motor is composed of a stator and a rotor and the interactions of those components are believed to generate the torque. Na+ influx through the PomA/PomB stator complex of Vibrio alginolyticus is coupled to torque generation and is speculated to trigger structural changes in the cytoplasmic domain of PomA that interacts with a rotor protein in the C-ring, FliG, to drive the rotation. In this study, we tried to overproduce the cytoplasmic loop of PomA (PomA-Loop), but it was insoluble. Thus, we made a fusion protein with a small soluble tag (GB1) which allowed us to express and characterize the recombinant protein. The structure of the PomA-Loop seems to be very elongated or has a loose tertiary structure. When the PomA-Loop protein was produced in E. coli, a slight dominant effect was observed on motility. We conclude that the cytoplasmic loop alone retains a certain function.