Comment | The Zinc (Zn2+)-Iron (Fe2+) Permease (ZIP) Family (TC 2.A.5)
Members of the ZIP family consist of proteins with eight putative transmembrane spanners. They are derived from animals, plants and yeast. They
comprise a diverse family, with several paralogues in any one organism (e.g., at least five in Caenorabditis elegans, at least five in Arabidopsis thaliana and two in
Saccharomyces cervisiae. The two S. cerevisiae proteins, Zrt1 and Zrt2, both probably transport Zn2+ with high specificity, but Zrt1 transports Zn2+ with ten-fold higher affinity
than Zrt2. Some members of the ZIP family have been shown to transport Zn2+ while others transport Fe2+, and at least one transports a range of metal ions. The energy source for
transport has not been characterized, but these systems probably function as secondary carriers.
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