Regulation of the Staphylococcus aureus plasmid p1258 mercury resistance operon

Experiments involving fusion between the Staphylococcus aureus plasmid p1258-encoded mer operon and the reporter gene β-lactamase, mutational analysis, and trans-complementation studies have shown that the merR gene of p1258, which shows DNA sequence similarity with known merR genes from other bacteria, regulates the expression of the mer operon in vivo. The merR gene product is a trans-acting protein that activates mer operon transcription in the presence of the inducers Hg²⁺ and Cd²⁺. A glutathione-S-transferase- MerR fusion protein specifically bound and protected a 27-nucleotide operator sequence from DNase I digestion. This operator sequence is highly homologous with mer operator sequences of other known systems.