Mouse Mt1 binds 7 atoms of divalent cadmium (Zangger et al. 1999, Tio et al. 2004, Artells et al. 2013). The mMt1 isoform exhibits metal ion binding abilities distinct from those of mMt2, with mMt2 showing a clear preference for Zn(II) coordination, if compared to Cu(I) or even to Cd(II). This is in full agreement with the gene expression regulation pattern for the Mt1 and Mt2 genes, as well as with the hypothesized preferential role of mMt2 in Zn(II) homeostasis mechanisms, while Mt1, possibly differentiated from a most recent duplication event in the mammalian metallothionein gene cluster, would have evolved to detoxify Cd(II), and probably other divalent metal ions (Artells et al, 2013).