RRC ID 30074
Author Grossman AD, Burgess RR, Walter W, Gross CA.
Title Mutations in the Ion gene of E. coli K12 phenotypically suppress a mutation in the sigma subunit of RNA polymerase.
Journal Cell
Abstract We have isolated spontaneous temperature-resistant revertants of a temperature-sensitive mutation (rpoD800) in the sigma subunit of E. coli K12 RNA polymerase. These revertants still contained the rpoD800 allele. They were mucoid, and sensitive to ultraviolet light and the radiomimetic agent nitrofurantoin, which are characteristics of lon mutants. One revertant, Tr29, was mapped to the lon region of the chromosome. Lon- rpoD800 double mutants were constructed, and were phenotypically indistinguishable from the spontaneous temperature-resistant revertant. It is the degradation-deficient property of lon mutants that is responsible for the suppression of the temperature-sensitive phenotype. We show that the rpoD800 sigma polypeptide is a substrate for the ion proteolytic system, and that mutations in lon decrease the rate of mutant sigma degradation. The rate of synthesis of mutant sigma was also affected in lon- strains. The net effect of lon-mutations was to increase the concentration of mutant sigma. We conclude that the temperature-sensitive phenotype results from insufficient concentration, rather than altered function, of the mutant protein.
Volume 32(1)
Pages 151-9
Published 1983-1
PII 0092-8674(83)90505-6
PMID 6337720
MeSH Bacterial Proteins / biosynthesis Escherichia coli / genetics* Genes, Bacterial* Kinetics Mutation Phenotype Sigma Factor / biosynthesis Sigma Factor / genetics* Suppression, Genetic Transcription Factors / genetics*
IF 31.398
Times Cited 74
Prokaryotes E. coli ME8282 ME8283