title: Cloning and DNA sequence of the mercuric- and organomercurial-resistance determinants of plasmid pDU1358.
abstract: The broad-spectrum mercurial-resistance plasmid pDU1358 was analyzed by cloning the resistance determinants and preparing a physical and genetic map of a 45-kilobase (kb) region of the plasmid that contains two separate mercurial-resistance operons that mapped about 20 kb apart. One encoded narrow-spectrum mercurial resistance to Hg2+ and a few organomercurials; the other specified broad-spectrum resistance to phenylmercury and additional organomercurials. Each determinant governed mercurial transport functions. Southern DNA X DNA hybridization experiments using gene-specific probes from the plasmid R100 mer operon indicated close homology with the R100 determinant. The 2153 base pairs of the promoter-distal part of the broad-spectrum Hg2+-resistance operon of pDU1358 were sequenced. This region included the 3'-terminal part of the merA gene, merD, unidentified reading frame URF1, and a part of URF2 homologous to previously sequenced determinants of plasmid R100. Between the merA and merD genes, an open reading frame encoding a 212 amino acid polypeptide was identified as the merB gene that determines the enzyme organomercurial lyase that cleaves the C--Hg bond of phenylmercury.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D005796:Genes; D005798:Genes, Bacterial; D008190:Lyases / Q000235:genetics*; D008628:Mercury / Q000494:pharmacology*; D009693:Nucleic Acid Hybridization; D009941:Organomercury Compounds / Q000494:pharmacology*; D011815:R Factors; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D009941:Organomercury Compounds; D004262:DNA Restriction Enzymes; D001616:beta-Galactosidase; D008190:Lyases; C050953:alkylmercury lyase; D008628:Mercury