Regulation of cadmium uptake by Saccharomyces cerevisiae.

In this work, we verified that yeast cells deleted in ZRT1 were not capable of transporting cadmium, suggesting that the transport of this metal into the cell would be carried out through this zinc transporter. On the other hand, cadmium absorption shown by a Deltagsh1 strain (a mutant not able of synthesizing glutathione) was twofold higher than in the control strain. Moreover, the deletion of YCF1 (which encodes a vacuolar glutathione S-conjugate pump) impaired the transport of this metal significantly. Using a mutant strain deficient in YAP1, which codifies a transcription factor that controls the expression of both GSH1 and YCF1, we also observed a twofold increase in cadmium uptake, the same behavior shown by Deltagsh1 cells. Cadmium is compartmentalized in vacuoles through the Ycf1 transporter, in the form of a bis-glutathionato-cadmium complex. We propose that gsh1 cells are unable to form the Cd-GS(2) complex, while ycf1 cells would accumulate high levels of this complex in the cytoplasm. In face of these results we raised the hypothesis that Cd-GS(2) complex controls cadmium uptake through the Zrt1 protein.