title: Nitrite transport is mediated by the nitrite-specific high-affinity NitA transporter and by nitrate transporters NrtA, NrtB in Aspergillus nidulans.
abstract: Disruption of the Aspergillus nidulans high-affinity nitrate transporter genes (nrtA and nrtB) prevents growth on nitrate but not nitrite. We identified a distinct nitrite transporter (K(m)=4.2+/-1 microM, V(max)=168+/-21 nmolmg(-1)DW(-1)h(-1)), designated NitA. Disruption of nrtA, nrtB and nitA blocked growth on nitrite, despite low rates of nitrite depletion we ascribe to passive nitrous acid permeation. Growth of the single mutant nitA16 on nitrite was wild-type, suggesting that NrtA and/or NrtB transports nitrite as well as nitrate. Indeed, NrtA and NrtB transport nitrite at higher rates than NitA; K(m) and V(max) values were 16+/-4 microM and 808+/-67 nmolmg(-1)DW(-1)h(-1) (NrtA) and 11+/-1 microM and 979+/-17 nmolmg(-1)DW(-1)h(-1) (NrtB). We suggest that NrtA is a nitrate/nitrite transporter, NrtB absorbs nitrite in preference to nitrate and NitA is exclusively a nitrite transporter.
authors.affiliation: Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada.
authors.forename: Ye
authors.initials: Y
authors.lastname: Wang
authors.forename: Wenbin
authors.initials: W
authors.lastname: Li
authors.forename: Yaeesh
authors.initials: Y
authors.lastname: Siddiqi
authors.forename: Vicki F
authors.initials: VF
authors.lastname: Symington
authors.forename: James R
authors.initials: JR
authors.lastname: Kinghorn
authors.forename: Shiela E
authors.initials: SE
authors.lastname: Unkles
authors.forename: Anthony D M
authors.initials: AD
authors.lastname: Glass
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D001233:Aspergillus nidulans / Q000254:growth & development / Q000378:metabolism*; D001693:Biological Transport, Active; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal / Q000235:genetics; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*
chemical_list: D027321:Anion Transport Proteins; D005656:Fungal Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D009573:Nitrites