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Hinge‐helix formation and DNA bending in various lac repressor–operator complexes
Author(s) -
Spronk Christian A. E. M.,
Folkers Gert E.,
Noordman AnneMarie G. W.,
Wechselberger Rainer,
van den Brink Nienke,
Boelens Rolf,
Kaptein Robert
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.22.6472
Subject(s) - biology , repressor , lac repressor , hinge , dna , operator (biology) , helix (gastropod) , genetics , biophysics , gene , transcription factor , physics , paleontology , classical mechanics , snail
The hinge‐region of the lac repressor plays an important role in the models for induction and DNA looping in the lac operon. When lac repressor is bound to a tight‐binding symmetric operator, this region forms an α‐helix that induces bending of the operator. The presence of the hinge‐helices is questioned by previous data that suggest that the repressor does not bend the wild‐type operator. We show that in the wild‐type complex the hinge‐helices are formed and the DNA is bent, similar to the symmetric complex. Furthermore, our data show differences in the binding of the DNA binding domains to the half‐sites of the wild‐type operator and reveal the role of the central base‐pair of the wild‐type operator in the repressor–operator interaction. The differences in binding to the operator half‐sites are incorporated into a model that explains the relative affinities of the repressor for various lac operator sequences that contain left and right half‐sites with different spacer lengths.