Earlier in vitro[11], [12], [13], [14], [15], [16] and in silico[17] work has shown that Cu transfer from Atox1 to metal-binding domains (WD) of the Wilson disease protein and metal-binding domains (MK) of the Menkes protein proceeds via a copper-bridged hetero-dimer complex where the metal is shared between the two metal-binding sites (Figure 1). This evidence concerns the gene ATOX1 and Wilson disease.