The ferredoxin:NAD+ oxidoreductase (Rnf) from the acetogen Acetobacterium woodii requires Na+ and is reversibly coupled to the membrane potential
- The anaerobic acetogenic bacterium Acetobacterium woodii has a novel Na(+)-translocating electron transport chain that couples electron transfer from reduced ferredoxin to NAD(+) with the generation of a primary electrochemical Na(+) potential across its cytoplasmic membrane. In previous assays in which Ti(3+) was used to reduce ferredoxin, Na(+) transport was observed, but not a Na(+) dependence of the electron transfer reaction. Here, we describe a new biological reduction system for ferredoxin in which ferredoxin is reduced with CO, catalyzed by the purified acetyl-CoA synthase/CO dehydrogenase from A. woodii. Using CO-reduced ferredoxin, NAD(+) reduction was highly specific and strictly dependent on ferredoxin and occurred at a rate of 50 milliunits/mg of protein. Most important, this assay revealed for the first time a strict Na(+) dependence of this electron transfer reaction. The Km was 0.2 mm. Na(+) could be partly substituted by Li(+). Na(+) dependence was observed at neutral and acidic pH values, indicating the exclusive use of Na(+) as a coupling ion. Electron transport from reduced ferredoxin to NAD(+) was coupled to electrogenic Na(+) transport, indicating the generation of ΔμNa(+). Vice versa, endergonic ferredoxin reduction with NADH as reductant was possible, but only in the presence of ΔμNa(+), and was accompanied by Na(+) efflux out of the vesicles. This is consistent with the hypothesis that Rnf also catalyzes ferredoxin reduction at the expense of an electrochemical Na(+) gradient. The physiological significance of this finding is discussed. Background: Ferredoxin:NAD+-oxidoreductases (Rnf) found in many bacteria are novel ion-translocating electron transport chains. Results: A Na+ requirement for the reaction and its reversible coupling to the transmembrane Na+ gradient are demonstrated. Conclusion: Na+ is the coupling ion. Rnf not only generates a Na+ potential but also uses it to drive the reverse reaction. Significance: Evidence for a function of Rnf in ferredoxin reduction is provided.
Verfasserangaben: | Verena HessORCiDGND, Kai SchuchmannGND, Volker MüllerORCiD |
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URN: | urn:nbn:de:hebis:30:3-758880 |
DOI: | https://doi.org/https://doi.org/10.1074/jbc.M113.510255 |
ISSN: | 0021-9258 |
Pubmed-Id: | https://pubmed.ncbi.nlm.nih.gov/24045950 |
Titel des übergeordneten Werkes (Englisch): | Journal of biological chemistry |
Verlag: | American Society for Biochemistry and Molecular Biology Publications |
Verlagsort: | Bethesda, Md |
Dokumentart: | Wissenschaftlicher Artikel |
Sprache: | Englisch |
Datum der Veröffentlichung (online): | 04.01.2021 |
Jahr der Erstveröffentlichung: | 2013 |
Veröffentlichende Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Datum der Freischaltung: | 15.11.2023 |
Freies Schlagwort / Tag: | Bioenergetics/Electron Transfer Complex; Electron Transfer; Energy Metabolism; Enzyme Kinetics; Membrane Energetics; Membrane Transport; Oxidation-Reduction; Physiology; Rnf; Sodium Transport |
Jahrgang: | 288 |
Ausgabe / Heft: | 44 |
Seitenzahl: | 7 |
Erste Seite: | 31496 |
Letzte Seite: | 31502 |
HeBIS-PPN: | 516504932 |
Institute: | Biowissenschaften |
DDC-Klassifikation: | 5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie |
Sammlungen: | Universitätspublikationen |
Lizenz (Deutsch): | Creative Commons - CC BY - Namensnennung 4.0 International |