JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Atkinson, M R
Right arrow Articles by Ninfa, A J
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Atkinson, M R
Right arrow Articles by Ninfa, A J
J Bacteriol. 1992 July; 174(14): 4538-4548

research-article

Characterization of Escherichia coli glnL mutations affecting nitrogen regulation.

M R Atkinson and A J Ninfa

Department of Biochemistry, Wayne State University School of Medicine, Detroit, Michigan 48201.

ABSTRACT

Nitrogen regulator II (NRII), the product of the Escherichia coli glnL (ntrB) gene, regulates the activation of transcription of glnA and the Ntr regulon by catalyzing the phosphorylation and dephosphorylation of the transcription factor NRI. Previous results have indicated that under conditions of nitrogen excess, transcriptional activation is prevented by an NRI-phosphate phosphatase activity that is observed when NRII and another signal transduction protein known as PII (the glnB product) interact. The availability of PII for this interaction is controlled by a uridylytransferase/uridylyl-removing enzyme, encoded by glnD, that reversibly modifies PII in response to intracellular signals of nitrogen availability. Here we describe the isolation and characterization of missense mutations in glnL that suppress the Ntr- phenotype resulting from a leaky glnD mutation. The regulation of glnA expression in the pseudorevertants was found to vary from complete insensitivity to ammonia in some strains (GlnC phenotype) to nearly normal regulation by ammonia in other strains. Sequence analysis indicated that in 16 instances suppression was due to point mutations at 14 different sites; 10 different mutations resulting in a variety of phenotypes were identified in a cluster extending from codons 111 to 154 flanking the site of NRII autophosphorylation at His-139. Complementation experiments with multicopy plasmids encoding NRII or PII showed that suppression by GlnC glnL alleles was eliminated upon introduction of the plasmid encoding NRII but was not affected by introduction of the plasmid encoding PII. Conversely, suppression by certain glnL alleles that resulted in regulated expression of glnA was eliminated upon introduction of either the plasmid encoding NRII or that encoding PII. We hypothesize that mutants of the latter type result in a subtle perturbation of the NRII-PII interaction and suggest two possible mechanisms for their effects.

J Bacteriol. 1992 July; 174(14): 4538-4548




This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 1992 by the American Society for Microbiology. All rights reserved.