This Article Full Text Full Text (PDF) Supplemental material Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lin, P.-C. Articles by Steuber, J. Search for Related Content PubMed PubMed Citation Articles by Lin, P.-C. Articles by Steuber, J.

 Previous Article  |  Next Article 

Journal of Bacteriology, May 2007, p. 3902-3908, Vol. 189, No. 10
0021-9193/07/$08.00+0     doi:10.1128/JB.01651-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Quinone Reduction by the Na⁺-Translocating NADH Dehydrogenase Promotes Extracellular Superoxide Production in Vibrio cholerae ^,

Po-Chi Lin,¹ Karin Türk,² Claudia C. Häse,³ Günter Fritz,⁴ and Julia Steuber^1*

Biochemisches Institut, Universität Zürich, CH-8057 Zürich, Switzerland,¹ School of Engineering and Science, International University Bremen, D-28759 Bremen, Germany,² Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, Oregon 97331,³ Fachbereich Biologie, Universität Konstanz, D-78457 Konstanz, Germany⁴

Received 25 October 2006/ Accepted 13 February 2007

The pathogenicity of Vibrio cholerae is influenced by sodium ions which are actively extruded from the cell by the Na⁺-translocating NADH:quinone oxidoreductase (Na⁺-NQR). To study the function of the Na⁺-NQR in the respiratory chain of V. cholerae, we examined the formation of organic radicals and superoxide in a wild-type strain and a mutant strain lacking the Na⁺-NQR. Upon reduction with NADH, an organic radical was detected in native membranes by electron paramagnetic resonance spectroscopy which was assigned to ubisemiquinones generated by the Na⁺-NQR. The radical concentration increased from 0.2 mM at 0.08 mM Na⁺ to 0.4 mM at 14.7 mM Na⁺, indicating that the concentration of the coupling cation influences the redox state of the quinone pool in V. cholerae membranes. During respiration, V. cholerae cells produced extracellular superoxide with a specific activity of 10.2 nmol min^–1 mg^–1 in the wild type compared to 3.1 nmol min^–1 mg^–1 in the NQR deletion strain. Raising the Na⁺ concentration from 0.1 to 5 mM increased the rate of superoxide formation in the wild-type V. cholerae strain by at least 70%. Rates of respiratory H₂O₂ formation by wild-type V. cholerae cells (30.9 nmol min^–1 mg^–1) were threefold higher than rates observed with the mutant strain lacking the Na⁺-NQR (9.7 nmol min^–1 mg^–1). Our study shows that environmental Na⁺ could stimulate ubisemiquinone formation by the Na⁺-NQR and hereby enhance the production of reactive oxygen species formed during the autoxidation of reduced quinones.

---

* Corresponding author. Mailing address: Biochemisches Institut, Universität Zürich, CH-8057 Zürich, Switzerland. Phone: (41) 44 635 5567. Fax: (41) 44 635 5907. E-mail: steuber{at}bioc.unizh.ch

Published ahead of print on 23 February 2007.

Supplemental material for this article may be found at http://jb.asm.org/.

---

Journal of Bacteriology, May 2007, p. 3902-3908, Vol. 189, No. 10
0021-9193/07/$08.00+0     doi:10.1128/JB.01651-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.