ArgR-independent induction and ArgR-dependent superinduction of the astCADBE operon in Escherichia coli

For Escherichia coli, growth in the absence of ammonia is termed nitrogen limited and results in the induction of genes that assimilate other nitrogen sources, a response mediated by sigma(54) and nitrogen regulator I (NR(I), also called NtrC). The astCADBE operon, which is required for growth with...

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Bibliographic Details
Published in:Journal of bacteriology Vol. 184; no. 11; p. 2940
Main Authors: Kiupakis, Alexandros K, Reitzer, Larry
Format: Journal Article
Language:English
Published: United States 01.06.2002
Subjects:
Acyltransferases - genetics
Acyltransferases - metabolism
Arginine
Bacterial Proteins - genetics
Bacterial Proteins - physiology
Base Sequence
Culture Media
DNA Footprinting
DNA-Binding Proteins - genetics
DNA-Binding Proteins - metabolism
DNA-Directed RNA Polymerases - genetics
Escherichia coli - enzymology
Escherichia coli - genetics
Escherichia coli - growth & development
Escherichia coli Proteins
Gene Expression Regulation, Bacterial
Molecular Sequence Data
Nitrogen - metabolism
Operon
PII Nitrogen Regulatory Proteins
Promoter Regions, Genetic
Protein Binding
Repressor Proteins - genetics
Repressor Proteins - physiology
RNA Polymerase Sigma 54
Sigma Factor - genetics
Trans-Activators
Transcription Factors
Transcription, Genetic
ISSN:0021-9193
Online Access:Get more information
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Summary:For Escherichia coli, growth in the absence of ammonia is termed nitrogen limited and results in the induction of genes that assimilate other nitrogen sources, a response mediated by sigma(54) and nitrogen regulator I (NR(I), also called NtrC). The astCADBE operon, which is required for growth with arginine as the sole nitrogen source, is moderately expressed during general nitrogen limitation and maximally expressed in the presence of arginine. The operon is also induced in stationary phase. Primer extension analysis of E. coli revealed the presence of a sigma(54)-dependent promoter utilized in exponential phase during nitrogen limitation and a sigma(S)-dependent promoter active during stationary phase. We used an ast-lacZ fusion to show that arginine stimulates expression, that ArgR, the arginine repressor, enhances expression from both promoters but is not essential, and that transcription by the two forms of the RNA polymerase is competitive and mutually exclusive. We demonstrated the binding of RNA polymerase holoenzymes, NR(I), and ArgR to the promoter region in vitro. We also reconstituted transcription from both promoters with purified components, which confirmed the accessory role of ArgR for the sigma(54)-dependent promoter. Thus, the ast operon exhibits nitrogen source-specific induction that is unique for an NR(I)-dependent gene. The transcriptional regulation of the ast operon in E. coli differs from that in Salmonella enterica serovar Typhimurium, in which ArgR is required for ast operon expression.
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ISSN:0021-9193
DOI:10.1128/JB.184.11.2940-2950.2002