Selective transporter that mediates the uptake of Zn(2+) (    ). Plays an essential role for dietary zinc uptake from small intestine (By similarity). The Zn(2+) uniporter activity is regulated by zinc availability (, ). Exhibits also polyspecific binding and transport of Cu(2+), Cd(2+) and possibly Ni(2+) but at higher concentrations (, ).
Subcellular locations: Cell membrane, Recycling endosome membrane, Apical cell membrane
Colocalized with TFRC in the recycling endosomes. Cycles between endosomal compartments and the plasma membrane in response to Zn(2+) availability. Zn(2+) deficiency promotes accumulation of SLC39A4 on the surface membrane, whereas high extracellular Zn(2+) levels induce internalization of SLC39A4, but also trigger drastic removal of cellular SLC39A4 via proteasomal and lysosomal degradation pathways.
Highly expressed in kidney, small intestine, stomach, colon, jejunum and duodenum.