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Journal of Bacteriology, October 1999, p. 6332-6338, Vol. 181, No. 20
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Hybrid Motor with H+- and Na+-Driven Components Can Rotate Vibrio Polar Flagella by Using Sodium Ions

Yukako Asai,1 Ikuro Kawagishi,1 R. Elizabeth Sockett,2 and Michio Homma1,*

Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan,1 and Genetics Division, Clinical Laboratory Sciences, Nottingham University, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom2

Received 1 March 1999/Accepted 2 August 1999

The bacterial flagellar motor is a molecular machine that converts ion flux across the membrane into flagellar rotation. The coupling ion is either a proton or a sodium ion. The polar flagellar motor of the marine bacterium Vibrio alginolyticus is driven by sodium ions, and the four protein components, PomA, PomB, MotX, and MotY, are essential for motor function. Among them, PomA and PomB are similar to MotA and MotB of the proton-driven motors, respectively. PomA shows greatest similarity to MotA of the photosynthetic bacterium Rhodobacter sphaeroides. MotA is composed of 253 amino acids, the same length as PomA, and 40% of its residues are identical to those of PomA. R. sphaeroides MotB has high similarity only to the transmembrane region of PomB. To examine whether the R. sphaeroides motor genes can function in place of the pomA and pomB genes of V. alginolyticus, we constructed plasmids including both motA and motB or motA alone and transformed them into missense and null pomA-paralyzed mutants of V. alginolyticus. The transformants from both strains showed restored motility, although the swimming speeds were low. On the other hand, pomB mutants were not restored to motility by any plasmid containing motA and/or motB. Next, we tested which ions (proton or sodium) coupled to the hybrid motor function. The motor did not work in sodium-free buffer and was inhibited by phenamil and amiloride, sodium motor-specific inhibitors, but not by a protonophore. Thus, we conclude that the proton motor component, MotA, of R. sphaeroides can generate torque by coupling with the sodium ion flux in place of PomA of V. alginolyticus.

* Corresponding author. Mailing address: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan. Phone: 81-52-789-2991. Fax: 81-52-789-3001. E-mail: g44416a{at}nucc.cc.nagoya-u.ac.jp.

Journal of Bacteriology, October 1999, p. 6332-6338, Vol. 181, No. 20
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Hase, C. C., Fedorova, N. D., Galperin, M. Y., Dibrov, P. A. (2001). Sodium Ion Cycle in Bacterial Pathogens: Evidence from Cross-Genome Comparisons. Microbiol. Mol. Biol. Rev. 65: 353-370 [Abstract] [Full Text]  
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