title: A description of conformational transitions in the Pribnow box of the trp promoter of Escherichia coli.
abstract: Selective changes in the NMR parameters of the sequence of CGTACTAGTTAACTAGTACG, which corresponds to the trp operator of Escherichia coli, were observed as a function of temperature. The changes were localized to the sequence TTAA in the Pribnow box (underlined). Differential changes in chemical shift were analyzed in terms of a three-state model (states I, II, and III) to give the equilibrium constants, enthalpy changes, and populations. The midpoints of the first and second transitions were 9 and 30 degrees C, with enthalpy changes of 58 and 35 kcal/mol, respectively. Measurement of the spin-lattice and cross-relaxation rate constants at different temperatures allowed some structural conclusions to be drawn about the nature of the transitions. The line width of the H2 of A11 goes through a maximum at about 30 degrees C, indicating moderately fast exchange between the states. The rate constants for exchange at the midpoints were about 200 (I----II) and 250 (II----III) s-1. Taking these findings into account, we propose a mechanism for the interaction between RNA polymerase and the promoter. This mechanism can explain the temperature dependence observed for the initiation of transcription.
authors.affiliation: Stanford Magnetic Resonance Laboratory, Stanford University, California 94305.
authors.forename: J F
authors.initials: JF
authors.lastname: Lefèvre
authors.forename: A N
authors.initials: AN
authors.lastname: Lane
authors.forename: O
authors.initials: O
authors.lastname: Jardetzky
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D013816:Thermodynamics; D014364:Tryptophan / Q000096:biosynthesis
chemical_list: D004269:DNA, Bacterial; D014364:Tryptophan