title: LexA repressor induces operator-dependent DNA bending.
abstract: LexA, the repressor of the SOS system in Escherichia coli induces a substantial DNA bending upon interaction with the operator of the caa gene, which codes for the bacterial toxin colicin A. Analysis by gel electrophoresis of a family of DNA fragments of identical length, but bearing the caa operator at different positions, shows that DNA bending occurs close to or within the operator sequence upon LexA binding. In contrast, the interaction of LexA with the recA operator induces no detectable bending on 5% polyacrylamide gels. This difference between the two operators is likely to be due to an intrinsic bendability of the caa operator related to thymine tracts located on both sides of the operator. Such tracts do not exist in the recA operator. The free DNA fragments harbouring the caa operator show a slight tendency to bend even in the absence of the LexA repressor. The centre of this intrinsic bend is located close to or within the caa operator.
authors.affiliation: Centre de Biologie et de Biochimie Moléculaire, Marseille, France.
authors.forename: R
authors.initials: R
authors.lastname: Lloubès
authors.forename: M
authors.initials: M
authors.lastname: Granger-Schnarr
authors.forename: C
authors.initials: C
authors.lastname: Lazdunski
authors.forename: M
authors.initials: M
authors.lastname: Schnarr
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli; D005798:Genes, Bacterial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D012697:Serine Endopeptidases; D014157:Transcription Factors / Q000235:genetics*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D014157:Transcription Factors; D000099160:LexA Repressor Protein