Degradation Rate of Mitochondrial Proteins in Arabidopsis thaliana Cells

The turnover of the proteomes of organelles in plant cells are known to be governed by both whole cell and organelle-specific processes. However, the rate and specificity of this protein turnover has not been explored in depth to understand how it affects different organellar processes. Here we have used progressive ¹⁵N labeling of Arabidopsis cells, and focused on the turnover rate of proteins in mitochondria. We provide estimates of degradation rate (K_d) for 224 mitochondrial proteins, showing a range of over 50-fold in K_d. Protein complexes, most notably the respiratory chain complexes, had K_d values that were generally coordinated and we have interpreted these measurements to outline how protein K_d differs within protein complexes and between functional categories. The fastest turnover rates were reported for DNA/RNA metabolism enzymes, chaperones, and proteases.