Protein turnover of the cytosolic ribosome and proteasome and their biochemical changes in cells in response to oxidative stress

Protein turnover is crucial to maintain cellular function and development. Stable isotope labelling in Arabidopsis thaliana showed a slow degradation rate of most ribosomal (r) and proteasomal proteins but identified RACK1 and RPP0-like r-proteins with high degradation rates even under control conditions. Knockout of the RPP0-like rapidly degrading r-protein affected root growth. The degradation rates of most r-proteins were even slower following oxidative stress. Combining ribosome quantification and cellular protein synthesis rates showed ribosomes remained functional during oxidative stress. However, this stress caused changes in the abundance of specific r-protein isoforms and a faster degradation rate of the r-protein RPS14C.