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The interaction of the recognition helix of lac repressor with lac operator.
Author(s) -
Lehming N.,
Sartorius J.,
Niemöller M.,
Genenger G.,
WilckenBergmann B.,
MüllerHill B.
Publication year - 1987
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 - 10.1002/j.1460-2075.1987.tb02625.x
Subject(s) - lac repressor , biology , repressor , lac operon , genetics , operator (biology) , computational biology , gene , transcription factor , gene expression
We have constructed a system which allows systematic testing of repressor–operator interactions. The system consists of two plasmids. One of them carries a lac operon in which lac operator has been replaced by a unique restriction site into which synthetic operators can be cloned. The other plasmid carries the gene coding for the repressor, in our case a semisynthetic lacI gene of which parts can be exchanged in a cassette‐like manner. A galE host allows us to select for mutants which express repressors with altered specificities. Here we report the change of specificity in the lac system by changing residues 1 and 2 of the recognition helix of lac repressor. The specificity changes are brought about cooperatively by the change of both residues. Exchanges of just one residue broaden the specificity. Our results hint that the recognition helix of lac repressor may possibly have the opposite orientation to those in Lambda cro protein or 434 CI repressor.