CADC, THE TRANSCRIPTIONAL REGULATORY PROTEIN OF THE CADMIUM RESISTANCE SYSTEM OF STAPHYLOCOCCUS-AUREUS PLASMID PI258

The CadC protein from the cadA cadmium resistance operon of Staphyloco ccus aureus plasmid pI258 regulates transcription of this system in vi tro, The CadC protein was overproduced in Escherichia coil cells and p artially purified, Gel shift assays of the proposed cadA operator/prom oter region DNA shelved specific association with the CadC protein. Co ntrol arsenic resistance operator/promoter DNA from the same plasmid w as not shifted by the CadC protein, Cd2+, Bi3+, acid Pb2+ caused the r elease of CadC from DNA in gel retardation assays. DNase I footprintin g measurements showed that the CadC protein specifically associated wi th and protected a region of operator/promoter DNA from nucleotide pos itions -7 to +14 relative to the start point Of mRNA synthesis. Runoff transcription assays with the operator/promoter region of DNA (plus t he first 69 nucleotides of the cadC gene) and purified E. coli RNA pol ymerase gave an mRNA product of the predicted size. Added CadC protein inhibited transcription in vitro.