Nitrate transporter (IPR004737)

Short name: NO3_transporter

Overlapping homologous superfamilies


Family relationships


This family represents nitrate/nitrite antiporters in bacteria, fungi, algae and marine diatoms. Nitrate transporters in Escherichia coli are involved in excretion of nitrite produced by the dissimilatory reduction of nitrate. NarK is polytopic membrane protein with 12 transmembrane domains which is involved in nitrate uptake and nitrite excretion and is thought to function as a nitrate/nitrite antiporter [PMID: 18691156, PMID: 16391109]. 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 [PMID: 7934881].

In the opportunistic fungal pathogen Aspergillus fumigatus the nitrate transporter crnA clusters with nitrite reductase (niiA) and nitrate reductase (niaD). NiaD, niiA and crnA are induced by nitrate and repressed by ammonium at the transcriptional level [PMID: 9508795]. In Hebeloma cylindrosporum the nitrate transporter polypeptide (NRT2) is characterised by 12 transmembrane domains and presents both a long putative intracellular loop and a short C-terminal tail, two structural features which distinguish fungal high-affinity transporters from their plant homologues. Transcription is repressed by ammonium and strongly stimulated by nitrate but also by organic nitrogen or nitrogen deficiency.

GO terms

Biological Process

GO:0015706 nitrate transport
GO:0015707 nitrite transport

Molecular Function

GO:0015112 nitrate transmembrane transporter activity
GO:0015113 nitrite transmembrane transporter activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.