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Mechanism of Lac repressor switch‐off: orientation of the Lac repressor DNA‐binding domain is reversed upon inducer binding
Author(s) -
Kamashev Dimitrii E.,
Esipova Natalia G.,
Ebralidse Konstantin K.,
Mirzabekov A.D.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01153-6
Subject(s) - lac repressor , repressor , inducer , dna , lac operon , operator (biology) , binding site , biology , microbiology and biotechnology , chemistry , biochemistry , gene , transcription factor , plasmid
Lac repressor's DNA‐binding domains contain helix‐turn‐helix motif which, though similar to those of phage λ Cro protein, are oriented differently with respect to DNA: in the specific complexes with Lac operator, N termini of the repressor's subunits are facing inwards. We demonstrate that, in the presence of an inducer, the repressor's N termini cross‐link to the operator's outermost nucleotides. We suggest that the inducer fixes the repressor's DNA‐binding domains in the Cro‐type configuration and thus garbles its recognition surface. Since the Cro‐type configuration is perfectly suitable for binding the DNA, this also explains how the switched‐off repressor retains its non‐specific DNA‐binding.