title: The NtcA-activated amt1 gene encodes a permease required for uptake of low concentrations of ammonium in the cyanobacterium Synechococcus sp. PCC 7942.
abstract: In the unicellular cyanobacterium Synechococcus sp. PCC 7942, ammonium/methylammonium transport activity has been characterized but ammonium transport genes have not been described. The amt1 gene encoding a permease responsible for high-affinity [14C]methylammonium transport in Synechococcus sp. PCC 7942 was cloned and inactivated. The Amt1 permease appeared essential to take up ammonium when it was present at low concentrations in the external medium and might also be involved in recapture of ammonium leaked out from the cells. Expression of amt1, which was induced in the absence of ammonium and also influenced by the inorganic carbon supply, was dependent on the NtcA transcriptional regulator. The promoter of amt1 was found to exhibit the structure of NtcA-activated promoters, and specific binding of purified NtcA to amt1 promoter sequences was observed. The results of this study indicate that amt1 belongs to the NtcA regulon and that NtcA may respond to both nitrogen and carbon availability.
authors.affiliation: Instituto de Bioquı́mica Vegetal y Fotosı́ntesis, CSIC-Universidad de Sevilla, Avda. Américo Vespucio s/n, E-41092 Sevilla, Spain1.
authors.forename: Marı A F
authors.initials: MAF
authors.lastname: Vázquez-Bermúdez
authors.affiliation: Instituto de Bioquı́mica Vegetal y Fotosı́ntesis, CSIC-Universidad de Sevilla, Avda. Américo Vespucio s/n, E-41092 Sevilla, Spain1.
authors.forename: Javier
authors.initials: J
authors.lastname: Paz-Yepes
authors.affiliation: Instituto de Bioquı́mica Vegetal y Fotosı́ntesis, CSIC-Universidad de Sevilla, Avda. Américo Vespucio s/n, E-41092 Sevilla, Spain1.
authors.forename: Antonia
authors.initials: A
authors.lastname: Herrero
authors.affiliation: Instituto de Bioquı́mica Vegetal y Fotosı́ntesis, CSIC-Universidad de Sevilla, Avda. Américo Vespucio s/n, E-41092 Sevilla, Spain1.
authors.forename: Enrique
authors.initials: E
authors.lastname: Flores
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D026901:Membrane Transport Proteins; D000644:Quaternary Ammonium Compounds; D014157:Transcription Factors; C075617:ntcA protein, Synechococcus