title: Mutational analysis of MarR, the negative regulator of marRAB expression in Escherichia coli, suggests the presence of two regions required for DNA binding.
abstract: MarR, the negative regulator of the Escherichia coli multiple antibiotic resistance (marRAB) operon, is a member of a newly recognized family of regulatory proteins. The amino acid sequences of these proteins do not display any apparent homologies to the DNA binding domains of prokaryotic transcription regulators and a DNA binding motif for any one of the MarR homologues is currently unknown. In order to define regions of MarR required for DNA binding, mutant repressors, selected based on their ability to interfere with (negatively complement) the activity of wild-type MarR, were isolated. As determined using gel mobility shift assays, 13 out of 14 negative complementing mutants tested were unable to bind DNA in vitro. Three negative complementing alleles presumably specify truncated repressors and one of these proteins, a 120 residue MarR, can bind DNA in vitro. Most of the negative complementing mutations were clustered within two areas of MarR with features related to a helix-turn-helix DNA binding motif. These regions are presumed to be required for the DNA binding activity of the repressor.
authors.affiliation: Center for Adaptation Genetics and Drug Resistance and the Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: M N
authors.initials: MN
authors.lastname: Alekshun
authors.forename: Y S
authors.initials: YS
authors.lastname: Kim
authors.forename: S B
authors.initials: SB
authors.lastname: Levy
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; C080004:MarR protein, E coli; D012097:Repressor Proteins; C080003:multiple antibiotic resistance protein B