The yeast ZRT1 gene encodes the zinc transporter protein of a high-affinity uptake system induced by zinc limitation

The yeast Saccharomyces cerevisiae has two separate systems for zinc uptake. One system has high affinity for substrate and is induced in zinc-deficient cells, The second system has lower affinity and is not highly regulated by zinc status, The ZRT1 gene encodes the transporter for the high-affinity system, called Zrt1p. The predicted amino acid sequence of Zrt1p is similar to that of Irt1p, a probable Fe(II) transporter from Arabidopsis thaliana. Like Irt1p, Zrt1p contains eight potential transmembrane domains and a possible metal-binding domain, Consistent with the proposed role of ZRT1 in zinc uptake, overexpressing this gene increased high-affinity uptake activity, whereas disrupting it eliminated that activity and resulted in poor growth of the mutant in zinc-limited media, Furthermore, ZRT1 mRNA levels and uptake activity were closely correlated, as was zinc-limited induction of a ZRT1-lacZ fusion. These results suggest that ZRT1 is regulated at the transcriptional level by the intracellular concentration of zinc, ZRT1 is an additional member of a growing family of metal transport proteins.