Molecular
mechanisms regulating cadmium detoxification in Saccharomyces cerevisiae.
Elis Eleutherio (1),
Paula Adamis (2), Debora Gomes (2), Lilian Fragoso (2), Cristiano Riger (2),
Anita Panek (2)
(1) Department of Biochemistry, Institut of Chemistry, UFRJ, 21949-900, Rio de
Janeiro, Brazil (eliscael@iq.ufrj.br); (2) Biochemistry -Inst. Chemistry, UFRJ,
Brig. Trompowysk s/n, Rio de Janeiro RJ, 21949-900, Brazil
In this work, we verified that yeast cells deleted in ZRT1 were not capable of transporting cadmium, suggesting that the transport of cadmium into the cell would occur through this zinc transporter. On the other hand, cadmium absorption shown by a gsh1 strain (glutathione deficient) was 2-fold higher than in the control strain. Moreover, the deletion of YCF1 (which codes 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 2-fold increase in cadmium uptake, the same behaviour shown by gsh1 cells. Cadmium is compartmentalized in vacuoles through Ycf1, in the form of a bis-glutathionato-cadmium complex. We propose that gsh1 cells are unable to form the Cd-glutathione complex, while the ycf1 cells accumulated high levels of this complex in the cytoplasm. Additionally, we observed that cells deficient in the cytosolic superoxide dismutase (Sod1) removed 2-fold more metal than its parental strain. Control strain showed an increased GSSG/GSH (oxidized/ reduced form of glutathione) after expoure to cadmium, while in sod1 cells this relation did not change by the presence of the metal. In face of these results we raised the hypothesis that the Cd-glutathione complex controls cadmium uptake through the Zrt1 protein.