Dynamic Changes In Protein Abundance And Posttranslational Modification In Yeast Cells In Response To Environmental Stress

The ability of mass-spectrometry to identify and quantify peptides based on their mass to charge ratios is transforming protein measurements in light of whole genome sequencing and improved protein database search algorithms. We used quantitative mass spectrometry to investigate, on a whole proteome scale, the dynamic changes in protein abundance in response to oxidative cell stress by treating cells with hydrogen peroxide (H₂O₂). We globally examined how these changes are dependent on upstream activation of signaling pathways by protein phosphorylation. We used stable isotopes to differentially label proteins in two cell populations, one of which was treated with H₂O₂. Cells were harvested, lysed and protein extracted and digested with endoproteinase LysC. Peptide fractionation and phosphopeptide enrichment enabled the acquisition of low-abundance proteins and phosphorylation events. We correlated protein changes with those observed at the mRNA level. Preliminary results show potential discrepancies between mRNA abundance and protein content. The yeast Saccharomyces cerevisiae is capable of withstanding rapid environmental changes though natural acclimation process known as the environmental stress response (ESR). This involves a complex transformation of the mRNA expression profile that may not directly correlate to protein level.