2010
DOI: 10.1073/pnas.1002866107
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Energy transducing redox steps of the Na + -pumping NADH:quinone oxidoreductase from Vibrio cholerae

Abstract: Naþ -NQR is a unique respiratory enzyme that couples the free energy of electron transfer reactions to electrogenic pumping of sodium across the cell membrane. This enzyme is found in many marine and pathogenic bacteria where it plays an analogous role to the H þ -pumping complex I. It has generally been assumed that the sodium pump of Na þ -NQR operates on the basis of thermodynamic coupling between reduction of a single redox cofactor and the binding of sodium at a nearby site. In this study, we have defined… Show more

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Cited by 53 publications
(90 citation statements)
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References 31 publications
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“…NADH is oxidized in a two electron step at the FAD of subunit N q rF and electrons are transferred one by one from FAD to the [2Fe 2S] cluster residing at an edge to edge dis tance of9. 8 kinetics data indicate that the electrons are subsequently transferred to FMNNqr<: 16 • and via FMNNqrB> and riboflavillNqrB fmally to ubiquinone. However, FMNNqr<: resides in the periplasm and the electrons have to cross the cytoplasmic membrane, making direct electron transfer from NqrF to NqrC very unlikely.…”
Section: Electron Transfer Pathwaymentioning
confidence: 98%
See 1 more Smart Citation
“…NADH is oxidized in a two electron step at the FAD of subunit N q rF and electrons are transferred one by one from FAD to the [2Fe 2S] cluster residing at an edge to edge dis tance of9. 8 kinetics data indicate that the electrons are subsequently transferred to FMNNqr<: 16 • and via FMNNqrB> and riboflavillNqrB fmally to ubiquinone. However, FMNNqr<: resides in the periplasm and the electrons have to cross the cytoplasmic membrane, making direct electron transfer from NqrF to NqrC very unlikely.…”
Section: Electron Transfer Pathwaymentioning
confidence: 98%
“…Any movement ofhelix X would induce a movement of helix VIII as well. Previous studies 16 put forward that electron transfer from FMNNqrB to riboflavinNqrB is coupled to the release ofN a+ to the periplasm Oxidation of the FMNNqrB radical to the uncharged form might lead to the loss of the interaction between NS ofFMNNqrB and the helix dipole, thereby releasing helix X.…”
Section: Mechanism Of Na + Translocationmentioning
confidence: 99%
“…As can be observed, the increase in the fluorescence of RH421 correlates with the rise in the concentration of the five-electron reduced state of Na ϩ -NQR, corroborating the kinetic and stopped flow data. Following the burst in membrane potential generation, the fluorescence increased for several seconds (data not shown) at a steady state rate, indicating that the vesicles are Kinetic Mechanism of Na ؉ -NQR not leaky and have the ability to support a substantial membrane potential (Ͼ100 mV) (14,30).…”
Section: ؉ -Nqrmentioning
confidence: 99%
“…Although the crystallographic data offers new clues about the location of this cofactor, its binding site remains unidentified. Na ϩ -NQR belongs to a family of membrane-bound redoxdriven pumps that has evolved independently from the main families of respiratory enzymes and ion pumps (8), and it shows novel characteristics, such as distinctive folding patterns in some of its subunits (12), the use of riboflavin as a cofactor (27), and mechanisms of ion translocation that are very different compared with other respiratory enzymes (30). The studies that have been performed on this enzyme have clarified the stoichiometry of the reactions, the types of side reactions catalyzed by the enzyme, most substrate-and cofactor-binding sites, the pathway of electron transfer, the physicochemical properties of the cofactors, and some of the structures involved in sodium transport (4,5).…”
mentioning
confidence: 99%
“…The enzyme is an integral membrane complex consisting of six subunits (NqrA-F) encoded by the nqr operon (2). There is a consensus that the electron transfer takes place through a series of five redox cofactors as follows: a FAD; a 2Fe-2S center; two covalently bound FMN, and a riboflavin (3)(4)(5). Different studies have intensively investigated the locations and redox properties of the cofactors of the enzyme (6 -12); however, the exact locations of the ubiquinone-binding site(s) and the Na ϩ transport pathway, as well as the mechanism that couples Na ϩ transport to the electron transfer, still remain elusive.…”
mentioning
confidence: 99%