title: NarK is a nitrite-extrusion system involved in anaerobic nitrate respiration by Escherichia coli.
abstract: 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.
authors.affiliation: Department of Biology, University of Dayton, Ohio 45469-2320.
authors.forename: J J
authors.initials: JJ
authors.lastname: Rowe
authors.forename: T
authors.initials: T
authors.lastname: Ubbink-Kok
authors.forename: D
authors.initials: D
authors.lastname: Molenaar
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
mesh_terms: D000693:Anaerobiosis; D027321:Anion Transport Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D009573:Nitrites; D011510:Proteolipids; C020485:proteoliposomes