The cadmium-resistant gene, CAD2, which is a mutated putative copper-transporter gene (PCA1), controls the intracellular cadmium-level in the yeast S-cerevisiae

Yeast cells carrying the CAD2 gene exhibit a resistance to cadmium. We cloned this gene and demonstrated that it was a mutated form derived from the gene of a putative copper-transporting ATPase (PCA1). By site-directed mutagenesis, it appeared that the mutation conferring cadmium resistance was a R970G-substitution in the C-terminal region of Peal protein. The intracellular cadmium level of cells carrying CAD2 was lower than that of cells carrying either PCA1 or Delta cad2. Furthermore, cells with overexpression of CAD2 showed a much lower intracellular cadmium level than that of cells with a single-copy CAD2. From these results, we conclude that the Cad2 protein controls the intracellular cadmium level through an enhanced cadmium efflux system.