Thermodynamic contribution to the regulation of electron transfer in the Na(+)-pumping NADH:quinone oxidoreductase from Vibrio cholerae |
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Authors: | Neehaul Yashvin Juárez Oscar Barquera Blanca Hellwig Petra |
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Institution: | Laboratoire de spectroscopie vibrationnelle et electrochimie des biomolecules, Institut de Chimie, UMR 7177, Université de Strasbourg-CNRS, 67070 Strasbourg, France. |
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Abstract: | The Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR) is a fundamental enzyme of the oxidative phosphorylation metabolism and ionic homeostasis in several pathogenic and marine bacteria. To understand the mechanism that couples electron transfer with sodium translocation in Na(+)-NQR, the ion dependence of the redox potential of the individual cofactors was studied using a spectroelectrochemical approach. The redox potential of one of the FMN cofactors increased 90 mV in the presence of Na(+) or Li(+), compared to the redox potentials measured in the presence of other cations that are not transported by the enzyme, such as K(+), Rb(+), and NH(4)(+). This shift in redox potential of one FMN confirms the crucial role of the FMN anionic radicals in the Na(+) pumping mechanism and demonstrates that the control of the electron transfer rate has both kinetic (via conformational changes) and thermodynamic components. |
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