ZnT7, a novel mammalian zinc transporter, accumulates zinc in the Golgi apparatus

ZnT7, a novel member of the zinc transporter (ZnT) family, was identified by searching the expressed sequence tag (EST) databases with the amino acid sequence of ZnT1. Like the other ZnT proteins, the protein (387 amino acids) predicted from this gene contains six transmembrane domains and a histidine-rich loop between transmembrane domains IV and V. We show that Znt7 is widely transcribed in mouse tissues with abundant expression in the liver and small intestine and moderate expression in the kidney, spleen, brain, and lung. An affinity-purified antibody raised against the amino acids 299-315 of mouse ZnT7 specifically reacted with the proteins with apparent molecular masses of 85, 43, and 65 kDa in small intestine and lung tissues by Western blot analysis. Immunofluorescence microscope analysis reveals that ZnT7 is localized in the Golgi apparatus and cytoplasmic vesicles. Exposure of the ZnT7-expressing Chinese hamster ovary (CHO) cells to zinc causes an accumulation of zinc in the Golgi apparatus, suggesting that ZnT7 facilitates zinc transport from the cytoplasm into the Golgi apparatus.