Characterization of the interaction of the glp repressor of Escherichia coli K-12 with single and tandem glp operator variants.
The glp operons of Escherichia coli are negatively controlled by the glp repressor. Comparison of the repressor-binding affinities for consensus and altered consensus operators in vivo showed that all base substitutions at positions 3, 4, 5, and 8 from the center of the palindromic operator caused a striking decrease in repressor binding. Substitutions at other positions had a severe to no effect on repressor binding, depending on the base substitution. The results obtained indicate that the repressor binds with highest affinity to operators with the half-site WATKYTCGWW, where W is A or T, K is G or T, and Y is C or T. Strong cooperative binding of the repressor to tandem operators was demonstrated in vivo. Cooperativity was maximal when two 20-bp operators were directly repeated or when 2 bp separated the two operators. Cooperativity decreased with the deletion of 2 bp or the addition of 4 bp between the individual operators. Cooperativity was eliminated with a 6-bp insertion between the operators.
Zhao
N
N
Department of Biochemistry and Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061-0308.
Oh
W
W
Trybul
D
D
Thrasher
K S
KS
Kingsbury
T J
TJ
Larson
T J
TJ
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D015870:Gene Expression; D005798:Genes, Bacterial / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic / Q000502:physiology*; D009876:Operon / Q000502:physiology*; D018085:Regulon / Q000502:physiology; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins