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.