title: The mechanism of CAP-lac repressor binding cooperativity at the E. coli lactose promoter.
abstract: The cyclic AMP receptor protein (CAP) and lactose repressor bind their regulatory sites in the lactose promoter with moderate cooperativity (omega C101 = 11.8(+/- 3.7)). This cooperativity is significantly reduced by the removal of DNA located upstream of the CAP binding site or by substitution of the dimeric lacI-18 mutant repressor for the wild-type tetrameric protein. These results are consistent with a mechanism of interaction in which CAP bends the DNA and the lac repressor binds simultaneously to its operator site and to promoter-distal sequences. Similar values of omega C101 were obtained with a promoter truncation containing the O3 pseudooperator site and one in which the site is destroyed, suggesting that DNA contacts distal to the O3 site are necessary for cooperative binding.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Vossen
authors.forename: D F
authors.initials: DF
authors.lastname: Stickle
authors.forename: M G
authors.initials: MG
authors.lastname: Fried
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D007763:Lac Operon; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial; D012097:Repressor Proteins