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PMID:12003934

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Citation

Kiupakis, AK and Reitzer, L (2002) ArgR-independent induction and ArgR-dependent superinduction of the astCADBE operon in Escherichia coli. J. Bacteriol. 184:2940-50

Abstract

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.

Links

PubMed PMC135064

Keywords

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; RNA Polymerase Sigma 54; Repressor Proteins/genetics; Repressor Proteins/physiology; Sigma Factor/genetics; Trans-Activators; Transcription Factors; Transcription, Genetic

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ECOLI:ARGR

involved_in

GO:1900081: regulation of arginine catabolic process

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

ECOLI:ARGR

involved_in

GO:2000144: positive regulation of DNA-templated transcription, initiation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

Notes

See also

References

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