Degradation Rate of Mitochondrial Proteins in <i>Arabidopsis thaliana</i> 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 (Kd) for 224 mitochondrial proteins, showing a range of over 50-fold in Kd. Protein complexes, most notably the respiratory chain complexes, had Kd values that were generally coordinated and we have interpreted these measurements to outline how protein Kd differs within protein complexes and between functional categories. The fastest turnover rates were reported for DNA/RNA metabolism enzymes, chaperones, and proteases.已知植物细胞细胞器蛋白质组（proteome）的周转更新受全细胞水平及细胞器特异性过程的共同调控。然而，目前尚未对该蛋白质周转的速率与特异性展开深入探究，以阐明其对不同细胞器生物学过程的影响机制。本研究采用逐步15N标记拟南芥（Arabidopsis）细胞的实验策略，重点聚焦线粒体中蛋白质的周转速率。我们对224种线粒体蛋白质的降解速率（Kd）进行了估算，结果显示Kd值的变化跨度超过50倍。蛋白质复合物，尤其是呼吸链复合物，其Kd值整体呈现协同一致性；本研究通过解读这些测量数据，厘清了蛋白质Kd值在复合物内部以及不同功能类别间的差异规律。研究发现，DNA/RNA代谢酶、分子伴侣及蛋白酶的周转速率最快。