title: Redox-dependent sodium binding by the Na(+)-translocating NADH:quinone oxidoreductase from Vibrio harveyi.
abstract: Relaxation characteristics of the 23Na nuclei magnetization were used to determine the sodium-binding properties of the Na+-translocating NADH:quinone oxidoreductase from Vibrio harveyi (NQR). The dissociation constant of Na+ for the oxidized enzyme was found to be 24 mM and for the reduced enzyme about 30 microM. Such large (3 orders in magnitude) redox dependence of the NQR affinity to sodium ions shows that the molecular machinery was designed to use the drop in redox energy for creating an electrochemical sodium gradient. Redox titration of NQR monitored by changes in line width of the 23Na NMR signal at 2 mM Na+ showed that the enzyme affinity to sodium ions follows the Nernst law for a one-electron carrier with Em about -300 mV (vs SHE). The data indicate that energy conservation by NQR involves a mechanism modulating ion affinity by the redox state of an enzyme redox cofactor.
authors: Department of Molecular Energetics of Microorganisms, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia.
authors: Alexander V
authors: AV
authors: Bogachev
authors: Yulia V
authors: YV
authors: Bertsova
authors: Olli
authors: O
authors: Aitio
authors: Perttu
authors: P
authors: Permi
authors: Michael I
authors: MI
authors: Verkhovsky
mesh_terms: D000465:Algorithms; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D003067:Coenzymes / Q000378:metabolism; D004579:Electron Transport; D004734:Energy Metabolism; D017136:Ion Transport; D010084:Oxidation-Reduction; D011199:Potentiometry; D011808:Quinone Reductases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013816:Thermodynamics; D014733:Vibrio / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D003067:Coenzymes; D011994:Recombinant Proteins; D012964:Sodium; C084142:sodium-translocating NADH-quinone reductase; D011808:Quinone Reductases