Cd2+ accommodation by Saccharomyces cerevisiae.

The Cd2+ accommodation mechanism of S. cerevisiae has been examined. In a synthetic medium containing 1 microM CdSO4, cell proliferation was observed following a time lag period of approximately 18 h. During the time lag period, the cell number and viable cell count did not change and the cells did not excrete organic acid as a Cd-chelator, neither did they produce inorganic sulphide in the form of CdS. Whereas approximately 30% of Cd2+ taken up by Cd-accommodated cells was distributed in the cytosol, only a small percentage of Cd2+ was found in the cytosol of unaccommodated cells following 1 h incubation in 1 microM Cd-medium. Furthermore, some Cd2+ in the soluble fraction from Cd-accommodated cells was bound to low molecular weight (less than 30,000) protein(s), while unaccommodated cells only contained small amounts of these proteins. Therefore, it is proposed that Cd2+ binds to the low molecular weight protein(s) present in the cytosol, resulting in a decrease of Cd-toxicity, although the exact mechanism of accommodation is not clear.