Functional characterization and regulation of gadX, a gene en coding an AraC/XylS-like transcriptional activator of the Escherichia coli glutamic acid decarboxylase system (Articolo in rivista)

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Label
  • Functional characterization and regulation of gadX, a gene en coding an AraC/XylS-like transcriptional activator of the Escherichia coli glutamic acid decarboxylase system (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Alternative label
  • Tramonti A 1, Visca P 2, De Canio M 3, Falconi M 4, De Biase D 3. (2002)
    Functional characterization and regulation of gadX, a gene en coding an AraC/XylS-like transcriptional activator of the Escherichia coli glutamic acid decarboxylase system
    in Journal of bacteriology (Print)
    (literal)
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  • Tramonti A 1, Visca P 2, De Canio M 3, Falconi M 4, De Biase D 3. (literal)
Pagina inizio
  • 2603 (literal)
Pagina fine
  • 2613 (literal)
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  • The identification of the effectors involved in GadX activation provides further insight into the molecular circuitry underlying the glutamic acid-based acid stress response of E. coli. The paper is published in a valued international journal (impact factor 3.98). (literal)
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  • 184 (literal)
Rivista
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  • The paper describes the characterization and regulation of the gadX gene of the Escherichia coli chromosome which is involved in encoding glutamic acid decarboxylase (Gad), a major protein in the control of pH homeostasis. This is achieved by consuming intracellular H(+) and producing gamma-aminobutyric acid. GadX belongs to the AraC/XylS family of bacterial transcriptional regulators, known to be activators of functions as diverse as sugar catabolism, responses to stress, and virulence. (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • 1 CNR (C.S. sulla Biologia Molecolare) 2 Uni Roma Tre (Dipartimento di Biologia) 3 Uni Sapienza (Dipartimento di Scienze Biochimiche \"A. Rossi Fanelli\") 4 Uni Camerino (Dipartimento di Biologia MCA (literal)
Titolo
  • Functional characterization and regulation of gadX, a gene en coding an AraC/XylS-like transcriptional activator of the Escherichia coli glutamic acid decarboxylase system (literal)
Abstract
  • The Escherichia coli chromosome contains two distantly located genes, gadA and gadB, which encode biochemically undistinguishable isoforms of glutamic acid decarboxylase (Gad). The Gad reaction contributes to pH homeostasis by consuming intracellular H(+) and producinggamma-aminobutyric acid. This compound is exported via the protein product of the gadC gene, which is cotranscribed with gadB. Here we demonstrate that transcription of both gadA and gadBC is positively controlled by gadX, a gene downstream of gadA, encoding a transcriptional regulator belonging to the AraC/XylS family. The gadX promoter encompasses the 67-bp region preceding the gadX transcription start site and contains both RpoD and RpoS putative recognition sites. Transcription of gadX occurs in neutral rich medium upon entry into the stationary phase and is increased at acidic pH, paralleling the expression profile of the gad structural genes. However, P(T5)lacO-controlled gadX expression in neutral rich medium results in upregulation of target genes even in exponential phase, i.e., when the gad system is normally repressed. Autoregulation of the whole gad system is inferred by the positive effect of GadX on the gadA promoter and gadAX cotranscription. Transcription of gadX is derepressed in an hns mutant and strongly reduced in both rpoS and hns rpoS mutants, consistent with the expression profile of gad structural genes in these genetic backgrounds. Gel shift and DNase I footprinting analyses with a MalE-GadX fusion protein demonstrate that GadX binds gadA and gadBC promoters at different sites and with different binding affinities. (literal)
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