Mutants of Saccharomyces Cerevisiae Defective in Vacuolar Function Confirm a Role for the Vacuole in Toxic Metal Ion Detoxification

To directly define vacuolar role(s) in metal detoxification, we have examined the responses of vacuole-deficient mutants of Saccharomyces cerevisiae to several potentially toxic metals known to be mainly detoxified in the cytosol (Cu, Cd) or the vacuole (Co, Mn, Ni, Zn). Three mutants, deficient in targeting of vacuolar proteins, were used with JSR18 delta 1 being devoid of any vacuole-like structure while ScVatB and ScVatC were deficient in specific protein subunits of the V-ATPase. The results obtained show that the absence of a vacuole or a functional vacuolar H(+)-ATPase was associated with increased sensitivity and a largely decreased capacity of the vacuole-deficient strains to accumulate Zn, Mn, Co and Ni, confirming an essential role for the vacuole in detoxification of these metals. In addition, the lack of vacuolar involvement in detoxification of Cu and Cd was confirmed since these metals did not exhibit increased toxicity towards the vacuolar mutants nor were there significant differences in Cu or Cd accumulation between parental and mutant strains.