Promotion of Zn²⁺ Uptake by Al³⁺ in a Saccharomyces Cerevisiae Mutant that Lacks the ZRT1 Gene Encoding a High-Affinity Zn Transporter

Abstract

A Saccharomyces cerevisiae mutant (zrt1Δ) lacking the ZRT1 gene, which encodes a high-affinity Zn²⁺ transporter, scarcely thrived in a low-pH, low-phosphate medium because of Zn²⁺ deficiency. Supplementation of the medium with Al³⁺ restored growth to a level comparable to that of a wild-type strain. A metal determination study clearly demonstrated that Al³⁺ induced the incorporation of Zn²⁺ into zrt1Δ cells, probably through the low-affinity Zn²⁺ transporter Zrt2p, given that the zrt1Δzrt2Δ double mutant did not show Al-induced growth enhancement. Al³⁺ may have altered the speciation of Zn²⁺ in the medium, resulting in enhanced levels of free Zn²⁺. Alternatively, it might be that Zrt2p was degraded by endocytosis in the absence of Al³⁺ and Al³⁺ interfered with this process, resulting in enhanced Zn²⁺ accumulation.