The mechanism of antibiotic action. V. Effect of chloramphenicol, chlorotetracycline and oxytetracycline on the synthesis of glutamic acid decarboxylase in Escherichia coli and of tyrosine decarboxylase in Streptococcus faecalis

1955 ◽  
Vol 20 (2) ◽  
pp. 507-510 ◽  
Author(s):  
D. Grünberger ◽  
J. Škoda ◽  
F. Šorm
Keyword(s):  
Escherichia Coli ◽  
Glutamic Acid ◽  
Glutamic Acid Decarboxylase ◽  
Acid Decarboxylase ◽  
Tyrosine Decarboxylase ◽  
Streptococcus Faecalis ◽  
Antibiotic Action

scholarly journals Functional Characterization and Regulation of gadX, a Gene Encoding an AraC/XylS-Like Transcriptional Activator of the Escherichia coli Glutamic Acid Decarboxylase System

2002 ◽  
Vol 184 (10) ◽  
pp. 2603-2613 ◽  
Author(s):  
Angela Tramonti ◽  
Paolo Visca ◽  
Michele De Canio ◽  
Maurizio Falconi ◽  
Daniela De Biase
Keyword(s):  
Escherichia Coli ◽  
Glutamic Acid ◽  
Expression Profile ◽  
Glutamic Acid Decarboxylase ◽  
Target Genes ◽  
Functional Characterization ◽  
Acid Decarboxylase ◽  
Rich Medium ◽  
Structural Genes ◽  
Ph Homeostasis

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 producing γ-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, PT5 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.

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