title: Interaction of the trp repressor from Escherichia coli with a constitutive trp operator.
abstract: The interaction of the trp repressor from Escherichia coli with a 20 bp fragment of DNA (CGTACTGATT.AATCAGTACG) corresponding to a mutant trp operator was studied by c.d. in the presence and absence of the co-repressor, L-tryptophan, and as a function of the concentration of K+ and Na+ ions. The affinity of the repressor for the mutant operator in the presence of tryptophan is about three orders of magnitude lower than the wild-type sequence. Binding in the absence of tryptophan is about 100-fold weaker than to the wild-type. The dependence of the dissociation constant on the concentration of K+ or Na+ is weak [d(log Ks)/d(log[M+]) = 2.5], and independent of the cation, indicating that electrostatic interactions are not as important for this repressor as for others.
authors.affiliation: National Institute for Medical Research, The Ridgeway, Mill Hill, London, U.K.
authors.forename: L R
authors.initials: LR
authors.lastname: Chandler
authors.forename: A N
authors.initials: AN
authors.lastname: Lane
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D002942:Circular Dichroism; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D009154:Mutation; D009875:Operator Regions, Genetic / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D012097:Repressor Proteins / Q000235:genetics*; D012964:Sodium / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics*; D014364:Tryptophan / Q000494:pharmacology; D029968:Escherichia coli Proteins
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011188:Potassium; D012097:Repressor Proteins; D012964:Sodium; D014157:Transcription Factors; D014364:Tryptophan; C027190:TRPR protein, E coli; D029968:Escherichia coli Proteins