Metalloregulated expression of the ars operon.
The plasmid-borne arsenical resistance (ars) operon encodes an arsenical-translocating ATPase and confers resistance to antimonials and arsenicals in Escherichia coli by extrusion of the toxic compounds from the cytosol. The trans-acting regulatory ArsR protein was shown to bind to a fragment of DNA containing the ars promoter. Hybrid formation of the ArsR protein with a ArsR-beta-lactamase chimeric protein suggested that the active form of the ArsR repressor is a dimer. From footprinting analysis the binding site was defined as a region of imperfect dyad symmetry just upstream of the -35 site. In vivo the operon was derepressed by oxyions of +III oxidation state of arsenic, antimony, and bismuth, as well as arsenate (As(V)), whereas in vitro ArsR protein-operator interaction was reduced by each of those compounds except arsenate, as determined by gel retardation and DNase I and hydroxyl radical footprinting experiments. This indicates that arsenate is not a true inducer and must be reduced to arsenite in vivo to induce. An operator mutant obtained by deletion of the in vitro ArsR-protected DNA sequence exhibited constitutive ars promoter activity, demonstrating that the binding site is the functional target for the ArsR repressor in vivo.
Wu
J
J
Department of Biochemistry, Wayne State University School of Medicine, Detroit, Michigan 48201.
Rosen
B P
BP
D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D001152:Arsenicals / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins; D001483:Base Sequence; D003850:Deoxyribonuclease I; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
C489527:ArsR protein, E coli; D001152:Arsenicals; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D003850:Deoxyribonuclease I; D001618:beta-Lactamases; D000251:Adenosine Triphosphatases