Isolation and properties of enhancer‐bypass mutants of sigma 54

The N‐terminal activation domain of Escherichia coli sigma 54 was randomly mutated to provide a library of changes that might allow the required enhancer function to be bypassed. Five clones harbouring mutant sigma factors were obtained that exhibited this property in that they enhanced growth under...

Full description

Saved in:
Bibliographic Details
Published in:Molecular microbiology 1997-03, Vol.23 (5), p.987-995
Main Authors: Syed, Adeela, Gralla, Jay D.
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Amino Acid Sequence
Bacterial Proteins - isolation & purification
Cloning, Molecular
DNA-Binding Proteins - genetics
DNA-Binding Proteins - metabolism
DNA-Binding Proteins - pharmacology
DNA-Directed RNA Polymerases - genetics
Escherichia coli
Escherichia coli - genetics
Escherichia coli - growth & development
Escherichia coli Proteins
Gene Expression Regulation, Bacterial
Gene Library
Heparin - pharmacology
Leucine - genetics
Molecular Sequence Data
Mutagenesis
Nitrogen - metabolism
PII Nitrogen Regulatory Proteins
Plasmids
Polymerase Chain Reaction
Promoter Regions, Genetic
RNA Polymerase Sigma 54
Sequence Analysis, DNA
Sigma Factor - genetics
Trans-Activators - metabolism
Transcription Factors
Transcription, Genetic
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The N‐terminal activation domain of Escherichia coli sigma 54 was randomly mutated to provide a library of changes that might allow the required enhancer function to be bypassed. Five clones harbouring mutant sigma factors were obtained that exhibited this property in that they enhanced growth under nitrogen‐limiting conditions in cells lacking NtrC. DNA sequence analysis located all mutations to four leucines in a small region between amino acids 25 and 31. No mutant sigma factors retained the hydrophobic character of the leucine residues. Mutant sigma factors were shown to transcribe in vitro without the need for enhancer binding activator or ATP hydrolysis, confirming the in vivo phenotype. These and other data suggest that a very small set of leucines is critical for keeping polymerase function in check, allowing high responsiveness to physiological induction via enhancer proteins such as NtrC.
ISSN:0950-382X
1365-2958
DOI:10.1046/j.1365-2958.1997.2851651.x