title: Genetic identification of the DNA binding domain of Escherichia coli LexA protein.
abstract: 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.
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721.
authors.forename: A T
authors.initials: AT
authors.lastname: Thliveris
authors.forename: D W
authors.initials: DW
authors.lastname: Mount
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D009876:Operon; D010957:Plasmids; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000235:genetics; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D011938:Rec A Recombinases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein