Figure 2
Chromium causes accumulation of toxic protein aggregates. (a) Exponential phase cells of S. cerevisiae in YEPD medium were exposed to 9 or 12 mM CrO3 for 3 h, in either the absence or presence of 10 μg ml-1 cycloheximide (CHX) (the latter cells were also pre-incubated for 1 h with CHX before metal exposure). Viability (%) was subsequently determined according to colony-forming-unit counts, with reference to control cultures not exposed to Cr. (b) Protein was extracted from cells treated for 30 minutes with 0.5 mM CrO3 and an aggregated protein fraction (separated from soluble and membrane proteins) [49] was prepared from each sample. The data show protein determined in the aggregate fraction as a proportion of the total cellular protein. (c) Cells were cultured in YEPD medium that was either unsupplemented with protein (open circles), or supplemented with 24 μg ml-1 of the soluble (filled circles) or aggregated (squares) protein fractions isolated from cells that had been exposed to 0.2 mM CrO3 for 1 h. All values are means ± standard error of the mean from at least three independent determinations.