Na(+)-translocating NADH-quinone reductase of marine and halophilic bacteria

J Bioenerg Biomembr. 1993 Aug;25(4):385-91. doi: 10.1007/BF00762464.


The respiratory chain of marine and moderately halophilic bacteria requires Na+ for maximum activity, and the site of Na(+)-dependent activation is located in the NADH-quinone reductase segment. The Na(+)-dependent NADH-quinone reductase purified from marine bacterium Vibrio alginolyticus is composed of three subunits, alpha, beta, and gamma, with apparent M(r) of 52, 46, and 32 kDa, respectively. The FAD-containing beta-subunit reacts with NADH and reduces ubiquinone-1 (Q-1) by a one-electron transfer pathway to produce ubisemiquinones. In the presence of the FMN-containing alpha-subunit and the gamma-subunit, Q-1 is converted to ubiquinol-1 without the accumulation of free radicals. The reaction catalyzed by the alpha-subunit is strictly dependent on Na+ and is strongly inhibited by 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), which is tightly coupled to the electrogenic extrusion of Na+. A similar type of Na(+)-translocating NADH-quinone reductase is widely distributed among marine and moderately halophilic bacteria. The respiratory chain of V. alginolyticus contains another NADH-quinone reductase which is Na+ independent and has no energy-transducing capacity. These two types of NADH-quinone reductase are quite different with respect to their mode of quinone reduction and their sensitivity toward NADH preincubation.

Publication types

  • Comparative Study
  • Review

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Electron Transport*
  • Energy Metabolism
  • Flavin Mononucleotide / metabolism
  • Gram-Negative Bacteria / enzymology
  • Halobacterium / enzymology*
  • NAD / metabolism
  • NAD(P)H Dehydrogenase (Quinone) / metabolism
  • NADH Dehydrogenase / metabolism
  • Oxidation-Reduction
  • Oxidoreductases / metabolism
  • Protein Conformation
  • Quinone Reductases / antagonists & inhibitors
  • Quinone Reductases / chemistry
  • Quinone Reductases / metabolism*
  • Sodium / physiology*
  • Species Specificity
  • Ubiquinone / metabolism
  • Vibrio / enzymology*


  • Bacterial Proteins
  • NAD
  • Ubiquinone
  • Flavin Mononucleotide
  • Sodium
  • Oxidoreductases
  • duroquinol oxidase
  • sodium-translocating NADH-quinone reductase
  • NAD(P)H Dehydrogenase (Quinone)
  • Quinone Reductases
  • NADH Dehydrogenase