Eukaryotic zinc transporters and their regulation

The last ten years have witnessed major advances in our understanding of zi nc transporters and their regulation in eukaryotic organisms. Two families of transporters, the ZIP (Zrt-, Irt-like Protein) and CDF (Cation Diffusion Facilitator) families, have been found to play a number of important roles in zinc transport. These are ancient gene families that span all phylogene tic levels. The characterized members of each group have been implicated in the transport of metal ions, frequently zinc, across lipid bilayer membran es. This remarkable conservation of function suggests that other, as yet un characterized members of the family, will also be involved in metal ion tra nsport. Many of the ZIP family transporters are involved in cellular zinc u ptake and at least one member, the Zrt3 transporter of S. cerevisiae, trans ports stored zinc out of an intracellular compartment during adaptation to zinc deficiency. In contrast, CDF family members mediate zinc efflux out of cells or facilitate zinc transport into intracellular compartments for det oxification and/or storage. The activity of many of these transporters is r egulated in response to zinc through transcriptional and post-transcription al mechanisms to maintain zinc homeostasis at both the cellular and organis mal levels.