title: Evidence for multiple nitrate uptake systems in the yeast Hansenula polymorpha.
abstract: Hansenula polymorpha mutants disrupted in the high-affinity nitrate transporter gene (YNT1) are still able to grow in nitrate. To detect the nitrate transporter(s) responsible for this growth a strain containing disruption of the nitrate assimilation gene cluster and expressing nitrate reductase gene (YNR1) under the control of H. polymorpha MOX1 (methanol oxidase) promoter was used (FM31 strain). In this strain nitrate taken up is transformed into nitrite by nitrate reductase and excreted to the medium where it is easily detected. Nitrate uptake which is neither induced by nitrate nor repressed by reduced nitrogen sources was detected in the FM31 strain. Likewise, nitrate uptake detected in the strain FM31 is independent of both Ynt1p and Yna1p and is not affected by ammonium, glutamine or chlorate. The inhibition of nitrite extrusion by extracellular nitrite suggests that the nitrate uptake system shown in the FM31 strain could also be involved in nitrite uptake.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Grupo del Metabolismo del Nitrógeno-Consejo Superior de Investigaciones Científicas, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Canary Islands, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Machín
authors.forename: G
authors.initials: G
authors.lastname: Perdomo
authors.forename: M D
authors.initials: MD
authors.lastname: Pérez
authors.forename: N
authors.initials: N
authors.lastname: Brito
authors.forename: J M
authors.initials: JM
authors.lastname: Siverio
mesh_terms: D027321:Anion Transport Proteins; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002352:Carrier Proteins / Q000378:metabolism; D005800:Genes, Fungal / Q000502:physiology; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000494:pharmacology; D010843:Pichia / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015203:Reproducibility of Results
chemical_list: D027321:Anion Transport Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D009573:Nitrites; D009584:Nitrogen