Na+ translocation by the NADH:ubiquinone oxidoreductase (complex I) from Klebsiella pneumoniae

Mol Microbiol. 1999 Aug;33(3):590-8. doi: 10.1046/j.1365-2958.1999.01506.x.


Complex I is the site for electrons entering the respiratory chain and therefore of prime importance for the conservation of cell energy. It is generally accepted that the complex I-catalysed oxidation of NADH by ubiquinone is coupled specifically to proton translocation across the membrane. In variance to this view, we show here that complex I of Klebsiella pneumoniae operates as a primary Na+ pump. Membranes from Klebsiella pneumoniae catalysed Na+-stimulated electron transfer from NADH or deaminoNADH to ubiquinone-1 (0.1-0.2 micromol min-1 mg-1). Upon NADH or deaminoNADH oxidation, Na+ ions were transported into the lumen of inverted membrane vesicles. Rate and extent of Na+ transport were significantly enhanced by the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP) to values of approximately 0.2 micromol min-1 mg-1 protein. This characterizes the responsible enzyme as a primary Na+ pump. The uptake of sodium ions was severely inhibited by the complex I-specific inhibitor rotenone with deaminoNADH or NADH as substrate. N-terminal amino acid sequence analyses of the partially purified Na+-stimulated NADH:ubiquinone oxidoreductase from K. pneumoniae revealed that two polypeptides were highly similar to the NuoF and NuoG subunits from the H+-translocating NADH:ubiquinone oxidoreductases from enterobacteria.

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism
  • Biological Transport
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology
  • Detergents
  • Dimethylamines
  • Electron Transport
  • Electron Transport Complex I
  • Kinetics
  • Klebsiella pneumoniae / enzymology*
  • NAD / metabolism
  • NADH, NADPH Oxidoreductases / chemistry*
  • Peptide Fragments / chemistry
  • Potassium Chloride / pharmacology
  • Protons
  • Sequence Analysis
  • Sodium / metabolism*
  • Sodium Chloride / pharmacology
  • Sodium-Potassium-Exchanging ATPase / metabolism


  • Bacterial Outer Membrane Proteins
  • Detergents
  • Dimethylamines
  • Peptide Fragments
  • Protons
  • NAD
  • Sodium Chloride
  • dodecyldimethylamine oxide
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone
  • Potassium Chloride
  • Sodium
  • NADH, NADPH Oxidoreductases
  • Electron Transport Complex I
  • Sodium-Potassium-Exchanging ATPase