title: Quality and position of the three lac operators of E. coli define efficiency of repression.
abstract: Repression of the lac promoter may be achieved in two different ways: either by interference with the action of RNA polymerase or by interference with CAP activation. We investigated cooperative repression of the Escherichia coli lac operon by systematic conversion of its three natural operators (O1, O2 and O3) on the chromosome. We find that cooperative repression by tetrameric Lac repressor increases with both quality and proximity of the interacting operators. A short distance of 92 bp allows effective repression by two very weak operators (O3, O3). The cooperativity of lac operators is discussed in terms of a local increase of repressor concentration. This increase in concentration depends on flexible DNA which allows loop formation.
authors.affiliation: Institut für Genetik der Universität zu Köln, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Oehler
authors.forename: M
authors.initials: M
authors.lastname: Amouyal
authors.forename: P
authors.initials: P
authors.lastname: Kolkhof
authors.forename: B
authors.initials: B
authors.lastname: von Wilcken-Bergmann
authors.forename: B
authors.initials: B
authors.lastname: Müller-Hill
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004794:Enzyme Repression; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D004269:DNA, Bacterial; D012097:Repressor Proteins