背景资料：ZIP9 (Zinc transporter ZIP9, Solute carrier family 39 member 9) is a multi-pass (seven transmembrane regions) membrane protein that belongs to the ZIP transporter (TC 2.A.5) family. Zinc transporters all have transmembrane domains, and are encoded by two SLC (solute-linked carrier) gene families: ZnT (SLC30) and Zip (SLC39). There are at least 9 ZnT and 15 Zip transporters in human cells. Zip transporters are believed to increase intracellular zinc by promoting zinc uptake.