title: A basic tail increases repression by dimeric lac repressor.
abstract: Tetrameric Lac repressor achieves cooperative repression by binding simultaneously to O1 and to one of the auxiliary operators O2 or O3, thereby forcing the intervening DNA into a loop. Dimeric Lac repressor is not able to form DNA loops and consequently shows no cooperative repression. We constructed a dimeric Lac repressor mutant which exhibits increased repression to the lac operon that does not depend on specific operator-repressor-operator loops. This Lac repressor carries a synthetic tail of basic residues attached to its C terminus. With this construct, we observe an increase of the in vivo repression upon addition of auxiliary lac operators to a chromosomal lac operon controlled by O1. This suggests that the basic tail enables dimeric Lac repressor to enhance its repression by additional non-specific DNA contacts.
authors.affiliation: Institut für Genetik der Universität zu Köln, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Kolkhof
authors.forename: S
authors.initials: S
authors.lastname: Oehler
authors.forename: R
authors.initials: R
authors.lastname: Alex
authors.forename: B
authors.initials: B
authors.lastname: Müller-Hill
mesh_terms: D000595:Amino Acid Sequence; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007763:Lac Operon / Q000187:drug effects; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic / Q000187:drug effects*; D011485:Protein Binding; D011487:Protein Conformation; D015202:Protein Engineering; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins