Zinc transporter which regulates intracellular zinc levels (By similarity). Required for spermatogenesis in both hermaphrodites and males where it resides in an inactive form in immature sperm, spermatids, but is likely activated in response to reduced spe-4 and spe-6 function (By similarity). Upon activation, mediates the release of zinc from internal stores in spermatids into the cytoplasm (By similarity). The resulting increase in cytoplasmic zinc levels promotes spermatid activation and subsequent differentiation into mature motile sperm that are capable of fertilization (By similarity). Localizes to membranous organelles. Belongs to the ZIP transporter (TC 2.A.5) family. KE4/Catsup subfamily.