Facilitates the accumulation of zinc from the cytoplasm into intracellular vesicles, being a zinc-efflux transporter (By similarity). May be a major component for providing zinc to insulin maturation and/or storage processes in insulin-secreting pancreatic beta-cells. Homodimer. Associated with insulin and glucagon secretory granules. Expressed in endocrine pancreatic islet alpha and beta cells. May be more abundant in beta cells than in alpha cells. Expressed in cubical epithelium lining thyroid follicles (at protein level). In the adrenal gland, detected in the cortex, but not in the medulla (at protein level). Down-regulated by IL1B and IFNG. Contains a histidine-rich region, HXXXXXHNH-motif, which is a ligand for zinc. Belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family. SLC30A subfamily.