title: Characterization of emeA, a NorA homolog and multidrug resistance efflux pump, in Enterococcus faecalis.
abstract: We hypothesized that multidrug resistance efflux pumps (MDRs) may be contributing to the drug resistance of enterococci. We recently identified potential MDR-encoding genes in the Enterococcus faecalis V583 genome. Among the putative MDRs, we found a gene that encodes a NorA homolog and have characterized this enterococcal MDR in the present study. A mutant from which the enterococcal NorA homolog has been deleted has reduced resistance to several NorA substrates. Complementation of the deletion mutant with the wild-type gene verified the involvement of this enterococcal gene in resistance to ethidium bromide (EtBr) and norfloxacin. Known MDR inhibitors (reserpine, lansoprazole, and verapamil) inhibit the efflux of EtBr and norfloxacin in wild-type strain OG1RF. A fluorescence assay with EtBr allowed us to quantitate the efflux capability of the enterococcal NorA pump. On the basis of these results, we have named this enterococcal gene emeA (enterococcal multidrug resistance efflux).
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA.
authors.forename: B M
authors.initials: BM
authors.lastname: Jonas
authors.forename: B E
authors.initials: BE
authors.lastname: Murray
authors.forename: G M
authors.initials: GM
authors.lastname: Weinstock
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002876:Chromosomes, Bacterial / Q000235:genetics; D003470:Culture Media; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics*; D004996:Ethidium / Q000378:metabolism; D005816:Genetic Complementation Test; D007202:Indicators and Reagents; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D017931:DNA Primers; D004269:DNA, Bacterial; C445688:EmeA protein, Enterococcus faecalis; D007202:Indicators and Reagents; D026901:Membrane Transport Proteins; D004996:Ethidium