Cd2+uptake, Cd2+binding and loss of cell K+by a Cd-sensitive and a Cd-resistant strain ofSaccharomyces cerevisiae

Abstract

Uptake of Cd2+ into Cd-resistant cells was approximately four times lower than in Cd-sensitive cells of Saccharomyces cerevisiae. Binding of Cd2+ to the yeast cells increased during incubation of the cells in the presence of Cd2+. The increase in the binding was much higher for wild-type cells than for Cd-resistant cells. This increased binding is ascribed to permeabilization of part of the cells. There is no single relation between the relative rate of K+ efflux and the cellular Cd content as has been found previously for wild-type cells. The rates of K+ efflux were much less than those found for the wild-type cells. Only with short incubation periods of the cells with Cd2+ was the same dependence found between the efflux of K+ and the cellular Cd content for both types of cell. The discrepancies found after extended incubation of the cells with Cd2+ are ascribed to the fact that Cd-provoked K+ release proceeds via an all-or-nothing process and that K+ released from permeabilized cells can be reaccumulated in still intact cells. The latter proceeds more efficiently in Cd-resistant cells than in wild-type cells.