Cloning and sequence analysis of the mercury resistance operon of Streptomyces sp. Strain CHR28 reveals a novel putative second regulatory gene.
A DNA library of pRJ28, a large linear plasmid encoding mercury resistance, was constructed, and the mercury resistance genes were cloned. The 5,921-bp sequence was analyzed and showed a high degree of similarity to the Streptomyces lividans 1326 mercury resistance operon. Genes merR, merT, merP, and orfIV were found in a similar order and in a single transcription unit. merA and merB were found to be transcribed in the opposite direction to genes merR, merT, merP, and orfIV, as in S. lividans 1326. A novel putative regulatory gene, orfX, was found 22 bp downstream of merA. orfX encodes a 137-amino acid protein with a potential helix-turn-helix motif in the N-terminal domain, characteristic of the MerR family of transcriptional regulators. Transcriptional studies showed that orfX is cotranscribed with merA and merB. It is hypothesized that orfX plays a role in the regulation of the mercury resistance operon, probably by binding at the MerR operator site.
Ravel
J
J
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
DiRuggiero
J
J
Robb
F T
FT
Hill
R T
RT
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004352:Drug Resistance, Microbial / Q000235:genetics; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000187:drug effects / Q000235:genetics*
D008628:Mercury