title: Repressed multidrug resistance genes in Streptomyces lividans.
abstract: Multidrug resistance (MDR) systems are ubiquitously present in prokaryotes and eukaryotes and defend both types of organisms against toxic compounds in the environment. Four families of MDR systems have been described, each family removing a broad spectrum of compounds by a specific membrane-bound active efflux pump. In the present study, at least four MDR systems were identified genetically in the soil bacterium Streptomyces lividans. The resistance genes of three of these systems were cloned and sequenced. Two of them are accompanied by a repressor gene. These MDR gene sequences are found in most other Streptomyces species investigated. Unlike the constitutively expressed MDR genes in Escherichia coli and other gram-negative bacteria, all of the Streptomyces genes were repressed under laboratory conditions, and resistance arose by mutations in the repressor genes.
authors.affiliation: Institute of Genetics, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan.
authors.forename: Li-Fong
authors.initials: LF
authors.lastname: Lee
authors.forename: Yi-Jiun
authors.initials: YJ
authors.lastname: Huang
authors.forename: Carton W
authors.initials: CW
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004996:Ethidium / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D019450:Genes, MDR; D008969:Molecular Sequence Data; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013302:Streptomyces / Q000187:drug effects* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; D004996:Ethidium