Several gene loci with a possible involvement in cellular tolerance to copper have been identified. One such locus in eubacteria and archaebacteria, cutA, is thought to be involved in cellular tolerance to a wide variety of divalent cations other than copper. The cutA locus consists of two operons, of one and two genes. The CutA1 protein is a cytoplasmic protein, encoded by the single-gene operon and has been linked to divalent cation tolerance. It has no recognized structural motifs. This family also contains putative proteins from eukaryotes (human and Drosophila).