Transport of iron across the cell membrane is a tightly controlled process carried out by specific proteins in all living cells. In yeast and in mammals, a system formed by an enzyme with ferroxidase activity coupled to a membrane transporter supports iron uptake or iron efflux, respectively. Ferroxidase belongs to the family of blue multicopper oxidases, enzymes able to couple the one-electron oxidation of substrate(s) to full reduction of molecular oxygen to water. On the other hand, the permeases are widely different and are specific to Fe