An NADH:quinone oxidoreductase of the halotolerant bacterium Ba1 is specifically dependent on sodium ions |
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| Authors: | S Ken-Dror J K Lanyi B Schobert B Silver Y Avi-Dor |
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| Affiliation: | 1. Departments of Biology and Chemistry, Technion-Israel Institute of Technology, Haifa, Israel;2. Department of Physiology and Biophysics, University of California, Irvine, California 92717 USA;1. Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia;2. Smart and Sustainable Township Research Centre (SUTRA), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia;3. Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, USA;1. State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, 201620, Shanghai, PR China;2. College of Biological, Chemical Sciences and Engineering, Jiaxing University, 314001, Jiaxing, PR China |
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| Abstract: | The rate of NADH oxidation by inverted membrane vesicles prepared from the halotolerant bacterium Ba1 of the Dead Sea is increased specifically by sodium ions, as observed earlier in whole cells. The site of this sodium effect is identified as the NADH: quinone oxidoreductase, similarly to the other such system known, Vibrio alginolyticus (H. Tokuda and T. Unemoto (1984) J. Biol. Chem. 259, 7785-7790). Sodium accelerates quinone reduction severalfold, but oxidation of the quinol, with oxygen as terminal electron acceptor, is unaffected. The sodium-dependent pathway of quinone reduction exhibits higher apparent affinity to extraneous quinone (Q-2) than the sodium-insensitive pathway, and is specifically inhibited by 2-heptyl-4-hydroxyquinoline N-oxide. ESR spectra of the membranes contain a feature at g = 1.98 which is tentatively identified as one originating from semiquinone. This feature is increased by NADH and decreased by addition of Na+, suggesting that, as proposed from different kinds of evidence for the V. alginolyticus system, sodium affects the semiquinone reduction step. As in the other system, the site of sodium stimulation in Ba1 probably corresponds to the site of sodium translocation, which was shown earlier (S. Ken-Dror, R. Shnaiderman, and Y. Avi-Dor (1984) Arch. Biochem. Biophys. 229, 640-649) to be linked directly to a redox reaction in the respiratory chain. |
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