The yeast permease Acr3p is a dual arsenite and antimonite plasma membrane transporter

The Acr3p permease from the yeast Saccharomyces cerevisiae is a prototype member of the arsenical resistance-3 (Acr3) family of transporters, which are found in all domains of life. Remarkably little is known about substrate specificity, localization and regulation of Acr3 proteins. Here, we show that the yeast Acr3p mediates not only high-level resistance to arsenite but also moderate tolerance to antimonite. The acr3 deletion mutant shows increased sensitivity to antimonite. In addition, overexpression of the ACR3 gene complements antimonite sensitivity of cells lacking the vacuolar ABC transporter Ycf1p. Moreover, both antimonite and arsenite induce transcription of the ACR3 gene resulting in the accumulation of Acr3 transporter at the plasma membrane. However, antimonite is much weaker inducer of the ACR3 gene transcription comparing to arsenite. Interestingly, the presence of metalloids does not influence either stability of Acr3 protein or its intracellular localization suggesting that Acr3p is mainly regulated at the transcriptional level. Finally, transport experiments confirmed that Acr3p indeed mediates efflux of antimonite and thus possesses a dual arsenite and antimonite specificity.