Regulation of the operon responsible for broad-spectrum mercury resistance in Streptomyces lividans 1326.
The broad-spectrum mercury resistance of Streptomyces lividans 1326 is mediated by six open reading frames (orf). These are arranged in two divergently transcribed operons. The orfs mer A (mercuric reductase) and mer B (organolyase) form one of the two operons. These genes and their regulation were further studied by deletion analysis and transcriptional fusion to the reporter gene xylE in the plasmid pXE4. An increase in XylE activity in response to the presence of mercuric ions was observed. The function of ORF2 (MerT) and ORF3 (MerP) as mercury-specific transport proteins, previously postulated based on the structural features of the predicted proteins, was confirmed. Transcription of the mer genes starts within the intercistronic region and two divergent promoters were identified by S1 nuclease mapping. Expression of the genes was negatively regulated by the product of orf1, now called merR. The repressor function was confirmed by gel retardation assays. MerR, produced in Escherichia coli, bound to two sites (operators) in the fragment containing the promoter region between merA and merR. Addition of mercuric ions and phenylmercuric acetate prevented the binding of MerR.
Brünker
P
P
Institut für Industrielle Genetik, Universität Stuttgart, Germany.
Rother
D
D
Sedlmeier
R
R
Klein
J
J
Mattes
R
R
Altenbuchner
J
J
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D050557:Catechol 2,3-Dioxygenase; D027682:Cation Transport Proteins; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D049308:Dioxygenases; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008627:Mercuric Chloride / Q000494:pharmacology; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics*; D010105:Oxygenases / Q000235:genetics; D010662:Phenylmercuric Acetate / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013302:Streptomyces / Q000187:drug effects* / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; C051124:MerR protein, Bacteria; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C094115:mercury transport protein, bacterial; D008627:Mercuric Chloride; D010105:Oxygenases; D049308:Dioxygenases; D050557:Catechol 2,3-Dioxygenase; D008628:Mercury; D010662:Phenylmercuric Acetate