Author(s):Thliveris AT, Mount DW. Genetic identification of the DNA binding domain of Escherichia coli LexA protein. Proc Natl Acad Sci U S A. 1992 May 15;89(10):4500-4. PMID 1584782
Journal: Proceedings Of The National Academy Of Sciences Of The United States Of America, Volume 89, Issue 10, May 1992
Two genetic approaches were taken to define the DNA binding domain of LexA protein, the repressor of the Escherichia coli SOS regulon. First, several dominant negative lexA mutants defective in DNA binding were isolated. The mutations altered amino acids in a region similar to the helix-turn-helix, a DNA binding domain of other repressors and DNA binding proteins. Second, the region encoding the predicted DNA recognition helix was subjected to oligonucleotide-directed mutagenesis and mutant LexA proteins with altered or relaxed specificity for several recA operator positions were isolated. By examining the effects of a series of amino acid substitutions on repressor specificity, it was shown that a glutamic acid residue at position 45 in LexA protein is important for recognition of the first base pair (G.C) in the recA operator.