Proteome analysis of Saccharomyces cerevisiae under metal stress by two-dimensional differential gel electrophoresis

The defense mechanism by which cells combat metal stress remains poorly understood. By utilizing a newly developed technique-the differential gel electrophoresis (DIGE)-we evaluated the biological alterations of metal stress on Saccharomyces cerevisiae at its translational level. By simultaneously comparing the differential expression profiles of thousands of proteins as results of 15 different metal treatments, we were able to closely examine the response of a large number of proteins within the yeast proteome towards individual metals, as well as the response of the same proteins towards different metals. This, to our knowledge, is the first case which demonstrates the potential of DIGE as a high-throughput tool for large-scale proteome analysis. From our studies, where yeast cells were exhaustively treated with exogenous metals, 20-30% of all proteins detected showed statistically significant changes. According to different effects (up-/downregulation) of protein expression levels observed, we were able to tentatively divide the 15 metals into three groups. By mass spectrometric analysis, more than 50 protein spots were positively identified, both quantitatively and qualitatively. One of the proteins was identified to be Cu/Zn superoxide dismutase (SOD1), and its expression levels as a result of 15 different metal treatments was further examined in greater details. Significant changes in SOD1 expression were observed throughout all 15 DIGE gels.