title: Thermodynamic contribution to the regulation of electron transfer in the Na(+)-pumping NADH:quinone oxidoreductase from Vibrio cholerae.
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.
authors.affiliation: Laboratoire de spectroscopie vibrationnelle et electrochimie des biomolecules, Institut de Chimie, UMR 7177, Université de Strasbourg-CNRS, 67070 Strasbourg, France.
authors.forename: Yashvin
authors.initials: Y
authors.lastname: Neehaul
authors.forename: Oscar
authors.initials: O
authors.lastname: Juárez
authors.forename: Blanca
authors.initials: B
authors.lastname: Barquera
authors.forename: Petra
authors.initials: P
authors.lastname: Hellwig
mesh_terms: D000641:Ammonia / Q000378:metabolism; D005486:Flavin Mononucleotide / Q000378:metabolism; D008094:Lithium / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013816:Thermodynamics; D014734:Vibrio cholerae / Q000201:enzymology*
chemical_list: D000641:Ammonia; D005486:Flavin Mononucleotide; D008094:Lithium; D012964:Sodium; D016660:NAD(P)H Dehydrogenase (Quinone); D011188:Potassium