title: Synergy between Escherichia coli CAP protein and RNA polymerase in the lac promoter open complex.
abstract: Characterization of ternary complexes containing an Escherichia coli lac promoter DNA fragment, CAP protein and RNA polymerase, separated on non-denaturing polyacrylamide gels and footprinted in the gel slice, reveals a striking stabilization of CAP against dissociation in the open complex, compared to the CAP-DNA complex lacking RNA polymerase. The stabilization is lost when half a helical turn of DNA is inserted between CAP and polymerase sites, but is partially restored with an 11 base-pair insert; stimulation of transcription parallels the stabilization effect. This behavior suggests a direct protein-protein interaction. Comparison of initiation kinetics for wild-type and a mutant in which the P2 promoter has been inactivated shows that CAP both strengthens binding in the closed complex and accelerates isomerization to the open complex; the latter effect accounts for the bulk of the observed transcriptional activation.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
authors.forename: D C
authors.initials: DC
authors.lastname: Straney
authors.forename: S B
authors.initials: SB
authors.lastname: Straney
authors.forename: D M
authors.initials: DM
authors.lastname: Crothers
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D007700:Kinetics; D007763:Lac Operon; D009154:Mutation; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011506:Proteins; D011956:Receptors, Cell Surface; D014157:Transcription Factors; C481662:crp protein, E coli; D012321:DNA-Directed RNA Polymerases; D003850:Deoxyribonuclease I