Facilitates the accumulation of zinc from the cytoplasm into intracellular vesicles, being a zinc-efflux transporter. 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. In the endocrine pancreas, expressed in insulin-producing beta cells. Expressed at relatively high levels in subcutaneous fat tissue from lean persons; much lower levels in visceral fat, whether from lean or obese individuals, and in subcutaneous fat tissue from obese individuals. Expressed in peripheral blood mononuclear cells, including T-cells and B-cells, with great variation among individuals ranging from negative to strongly positive. Contains a histidine-rich region, HXXXXXHNH-motif, which is a ligand for zinc. Variant Trp-325 is a risk factor that confers susceptibility to diabetes mellitus, noninsulin-dependent (NIDDM) [MIM:125853]. Belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family. SLC30A subfamily.