NarK Is a Nitrite-Extrusion System Involved in Anaerobic Nitrate Respiration by Escherichia Coli

Mol Microbiol. 1994 May;12(4):579-86. doi: 10.1111/j.1365-2958.1994.tb01044.x.


Escherichia coli can use nitrate as a terminal electron acceptor for anaerobic respiration. A polytopic membrane protein, termed NarK, has been implicated in nitrate uptake and nitrite excretion and is thought to function as a nitrate/nitrite antiporter. The longest-lived radioactive isotope of nitrogen, 13N-nitrate (half-life = 9.96 min) and the nitrite-sensitive fluorophore N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide have now been used to define the function of NarK. At low concentrations of nitrate, NarK mediates the electrogenic excretion of nitrite rather than nitrate/nitrite exchange. This process prevents intracellular accumulation of toxic levels of nitrite and allows further detoxification in the periplasm through the action of nitrite reductase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anaerobiosis
  • Anion Transport Proteins*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biological Transport, Active
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Electron Transport
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Models, Biological
  • Nitrates / metabolism*
  • Nitrites / metabolism*
  • Proteolipids / metabolism


  • Anion Transport Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • Nitrates
  • Nitrites
  • Proteolipids
  • nitrate transporters
  • proteoliposomes