Fig. 7.

A model for hZIP1 as intracellular zinc sensor in Caco-2 cells. a Zinc is taken up from the extracellular environment by transporter X. To maintain intracellular zinc homoeostasis, endogenous hZIP1 regulates zinc release from zinc-containing vacuoles (zicosomes) into the cytoplasm in basal zinc and zinc-deficient conditions by utilising 2 cytoplasmic histidines as zinc concentration sensors. This transport is ceased following an increase in extracellular/cytoplasmic zinc levels as the hZIP1 sensors are saturated