Characterization of two mutant metJ proteins with reduced, temperature-dependent capacity to regulate Escherichia coli K-12 met regulon elements.
At 28 degrees C, but not at 34 or 42 degrees C, strains with the metJ193 allele repressed chromosomal met genes but not a plasmid-borne met promoter. Increasing the metJ193 gene dosage to two copies resulted in overrepression of chromosomal and plasmid-borne met promoters at 28 degrees C. Suppressing the metJ185 amber mutation with supF (tRNATyr) produced the MetJ185F protein. Strains producing MetJ185F repressed chromosomal met promoters but not a plasmid-borne met promoter at 42 degrees C. These are the first known defective MetJ proteins with documented temperature-dependent function.
Bala
G A
GA
Department of Microbiology, Miami University, Oxford, Ohio 45056.
Collier
C D
CD
Emmett
M R
MR
Johnson
J R
JR
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D010582:Bacteriophage lambda; D004926:Escherichia coli / Q000235:genetics*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D009154:Mutation; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D013696:Temperature; D014157:Transcription Factors / Q000502:physiology*
D001426:Bacterial Proteins; D012097:Repressor Proteins; D014157:Transcription Factors