Genetic and biochemical analysis of the MetR activator-binding site in the metE metR control region of Salmonella typhimurium.
The Salmonella typhimurium metE and metR genes share a common control region, with overlapping, divergently transcribed promoters. A double gene fusion was constructed in which the metE promoter directs expression of the Escherichia coli lacZ gene and the metR promoter directs expression of the E. coli galK gene. By using an E. coli strain lysogenized with a lambda bacteriophage carrying the metE-lacZ metR-galK double fusion (lambda Elac.Rgal), two classes of cis-acting mutations were isolated that increase metR-galK expression. The first class of mutations causes a simultaneous decrease in metE-lacZ expression by disrupting the normal MetR-mediated activation of the metE promoter. The mutations are located within a region extending from 17 to 34 base pairs upstream of the -35 region of the metE promoter. Gel mobility shift assays and DNaseI protection experiments demonstrated that the MetR protein specifically binds to a 24-base-pair region encompassing these mutations. The second class of mutations increases metR-galK expression by directly altering the promoter consensus sequences of the metE and metR promoters.
Urbanowski
M L
ML
Department of Microbiology, University of Iowa, Iowa City 52242.
Stauffer
G V
GV
D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000502:physiology*; D003850:Deoxyribonuclease I; D015964:Gene Expression Regulation, Bacterial; D006710:Homocysteine / Q000502:physiology; D008715:Methionine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D012486:Salmonella typhimurium / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D014157:Transcription Factors; D006710:Homocysteine; D008715:Methionine; D003850:Deoxyribonuclease I