Abstract
The isolation and characterization of altered repressors of the lac operon which have an increased affinity for an operator should give useful clues about the molecular basis for the very tight and specific interaction between repressor and operator. A selection system has been devised which allows the isolation of such repressor mutants. This system selects for mutant repressors which can overcome lac operator-constitutive (Oc) mutations. By using in vivo assays, 24 candidates were obtained which, compared with wild type, have an increased trans effect of their repressor on one or several Oc operators. Three of these candidates have been investigated in vitro; the affinity of their repressor for inducer was unchanged, whereas the affinity for wild-type operator was increased 15-, 86-, and 262-fold, respectively.
MeSH Terms
Bacterial Proteins/isolation & purification,metabolism
Escherichia coli/genetics
Genes, Regulator
Lac Operon
Mutation
Repressor Proteins/isolation & purification,metabolism
Transcription Factors/metabolism
beta-Galactosidase/biosynthesis
Chemicals
Bacterial Proteins
Repressor Proteins
Transcription Factors
beta-Galactosidase
Authors & Affiliations
1 authors, click to expand affiliations / ORCID
Pfahl M
References (16)
16 references, click to expand
-
Genetic studies of the lac repressor. V. Repressors which bind operator more tightly generated by suppression and reversion of nonsense mutations.
J Mol Biol. 1978 Aug 15;123(3):431-54
PMID: 211238
-
Pseudoreversion of lactose operator-constitutive mutants.
J Bacteriol. 1977 Apr;130(1):100-6
PMID: 323217
-
Effect of DNA denaturants on the lac repressor-operator interaction.
Biochim Biophys Acta. 1978 Sep 27;520(2):285-90
PMID: 361087
-
Lac repressor-operator interaction. V. Characterization of super- and pseudo-wild-type repressors.
J Mol Biol. 1972 Feb 28;64(1):181-99
PMID: 4552482
-
Genetic map of the lactose repressor gene (i) of Escherichia coli.
Genetics. 1972 Nov;72(3):393-410
PMID: 4566215
-
The lac repressor-operator interaction. VII. A repressor with unique binding properties: the X86 repressor.
J Mol Biol. 1972 Dec 14;72(1):139-52
PMID: 4567399
-
Genetic analysis of the active sites of lac repressor.
Genetics. 1974 Apr;76(4):669-79
PMID: 4599253
-
lac Repressor-operator interaction. IX. The binding of lac repressor to operators containing Oc mutations.
J Mol Biol. 1974 May 15;85(2):231-48
PMID: 4599687
-
The location of the repressor binding sites in the lac operon.
Proc Natl Acad Sci U S A. 1974 Jun;71(6):2314-8
PMID: 4601586
-
Lac repressor-operator interaction. I. Equilibrium studies.
J Mol Biol. 1970 Feb 28;48(1):67-83
PMID: 4915295
-
The lac repressor-operator interaction. 3. Kinetic studies.
J Mol Biol. 1970 Nov 14;53(3):401-17
PMID: 4924006
-
An unusual lac repressor mutant.
J Mol Biol. 1970 Nov 14;53(3):561-5
PMID: 4924012
-
The nature of lactose operator constitive mutations.
J Mol Biol. 1971 Jul 28;59(2):273-305
PMID: 4935786
-
Tight-binding repressors of the lactose operon.
J Mol Biol. 1976 Aug 5;105(2):293-319
PMID: 787534
-
Isolation of pseudorevertants of lac oc mutants: selection system for superoperator mutations.
J Bacteriol. 1976 Oct;128(1):257-63
PMID: 789331
-
lac Repressor-operator interaction. Analysis of the X86 repressor mutant.
J Mol Biol. 1976 Sep 25;106(3):857-69
PMID: 789900