Zinc transporter which regulates intracellular zinc levels (PubMed:29879108). 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 (PubMed:29879108). Upon activation, mediates the release of zinc from internal stores in spermatids into the cytoplasm (PubMed:29879108). The resulting increase in cytoplasmic zinc levels promotes spermatid activation and subsequent differentiation into mature motile sperm that are capable of fertilization (PubMed:29879108). Localizes to membranous organelles. Highly expressed in developing spermatids (at the protein level) (PubMed:29879108). Expressed in the germline (PubMed:29879108). By cholesterol. Reduced brood size, but the majority of hermaphrodites are sterile and lay a large number of unfertilized oocytes (PubMed:29879108). Defective spermatid activation (PubMed:29879108). Double knockout with spe-4 results in failed spermatocyte division (PubMed:29879108). Double knockout with spe-6 results in suppression of the premature spermatid activation phenotype of the single spe-6 (hc163) mutant (PubMed:29879108). Belongs to the ZIP transporter (TC 2.A.5) family. KE4/Catsup subfamily.