title: The general amino acid permease of Rhizobium leguminosarum strain 3841 is negatively regulated by the Ntr system.
abstract: Cosmid-borne and chromosomal lacZ fusions to aapJ. aapQ and aapM were used to examine the nitrogen regulation of the general amino acid permease (Aap) of Rhizobium leguminosarum strain 3841. Transcription of the first gene of the operon (aapJ), which encodes the periplasmic binding protein, was 2-4-fold higher than aapQ and aapM, which encode the integral membrane proteins, under various growth conditions. This may be due to the presence of a putative stem loop in the intergenic region between aapJ and aapQ. All aap fusions were derepressed 3-5-fold after growth on glutamate as a nitrogen source, which effectively causes nitrogen limitation. An ntrC mutant was derepressed for transcription of the aap operon and had high rates of amino acid transport when grown on ammonia as the nitrogen source. Thus NtrC negatively regulates the aap operon, contrary to its usual role in positive gene activation. These results confirm that the aap-operon is subject to complex regulation involving both transcriptional and post-transcriptional factors.
authors.affiliation: School of Animal and Microbial Sciences, University of Reading, UK.
authors.forename: D L
authors.initials: DL
authors.lastname: Walshaw
authors.forename: C J
authors.initials: CJ
authors.lastname: Reid
authors.forename: P S
authors.initials: PS
authors.lastname: Poole
mesh_terms: D026905:Amino Acid Transport Systems; D000596:Amino Acids / Q000378:metabolism; D001426:Bacterial Proteins; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D026901:Membrane Transport Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D016961:Rhizobium leguminosarum / Q000201:enzymology*; D015534:Trans-Activators; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D026901:Membrane Transport Proteins; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D009584:Nitrogen