title: Emr, an Escherichia coli locus for multidrug resistance.
abstract: An Escherichia coli chromosomal DNA fragment cloned on a multicopy plasmid conferred resistance to carbonylcyanide m-chlorophenylhydrazone, nalidixic acid, and a number of other toxic compounds. The sequence of the cloned emr locus located at minute 57.5 of the chromosome revealed two open reading frames, emrA and emrB. emrB encodes a highly hydrophobic 56.2-kDa peptide, with 14 potential alpha-helices to span the inner membrane. The peptide is homologous to QacA, a multidrug-resistant pump from Staphylococcus aureus, and belongs to a gene family that includes tetracycline-resistant pumps of Gram-positive bacteria and the galactose/H+ symporter of E. coli. emrA encodes a putative 42.7-kDa peptide containing a single hydrophobic domain and a large C-terminal hydrophilic domain. An active pho-fusion to the C domain suggested that EmrA is a membrane protein. Disruption of emrB significantly increased sensitivity of cells to uncouplers. The cellular content of uncoupler increased in the order: overexpressed emrB cells greater than wild type greater than emrB-.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
authors.forename: O
authors.initials: O
authors.lastname: Lomovskaya
authors.forename: K
authors.initials: K
authors.lastname: Lewis
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000502:physiology; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D009268:Nalidixic Acid / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D013211:Staphylococcus aureus / Q000235:genetics; D013753:Tetracycline Resistance / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C489681:EmrA protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009570:Nitriles; D012333:RNA, Messenger; C100076:mesoxalonitrile; C068498:qacA protein, Staphylococcus aureus; C077168:emrA protein, Bacteria; C077169:VceB protein, Vibrio cholerae; D009268:Nalidixic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone