Open AccessMultiple Repressor Binding at the Operators in Bacteriophage λ
Author(s) -
Tom Maniatis,
Mark Ptashne
Publication year - 1973
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.70.5.1531
Subject(s) - repressor , operator (biology) , dna , nuclease , duplex (building) , base pair , bacteriophage , lac repressor , binding site , biology , microbiology and biotechnology , chemistry , genetics , gene , transcription factor , escherichia coli
Short DNA duplexes are protected when λ DNA is digested with nuclease in the presence of λ repressor. As the ratio of repressor to operator is increased, six successively larger fragments are recovered, ranging in size from 35 to 100 base pairs, each of which binds repressor. Study of these fragments indicates that, at each of the two λ operators (o L ando R ), repressor first binds to a unique site (not necessarily terminal), and that five additional sites are then filled in linear right-ward or left-ward order. The nucleotide sequences and affinities for repressor ofo L ando R are not identical, although six fragments of similar size are protected at each operator. Evidence is presented arguing against the existence of hairpin-like structures in the operator fragments, and, moreover, it is shown that the operator duplex does not unwind when repressor binds to it.