Manipulating protein conformations for exploring protein structure–function relationship has shown great promise. Although protein conformational changes under pulling force manipulation have been extensively studied, protein conformation changes under a compressive force have not been explored quantitatively. The latter is even more biologically significant and relevant in revealing protein functions in living cells associated with protein crowdedness, distribution fluctuations, and cell osmotic stress. Here we report our experimental observations on abrupt ruptures of protein native structures under compressive force, demonstrated and studied by single-molecule AFM-FRET spectroscopic nanoscopy. Our results show that the protein ruptures are abrupt and spontaneous events occurred when the compressive force reaches a threshold of 12–75 pN, a force amplitude accessible from thermal fluctuations in a living cell. The abrupt ruptures are sensitive to local environment, likely a general and important pathway of protein unfolding in living cells.

中文翻译：

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在picoNewton压缩力操纵下揭示蛋白质天然结构的突然和自发性破裂

操纵蛋白质构象以探索蛋白质的结构-功能关系已显示出巨大的希望。尽管已经对拉力操纵下的蛋白质构象变化进行了广泛的研究，但尚未定量研究在压缩力下的蛋白质构象变化。后者在生物学上具有更大的意义，并且在揭示活细胞中与蛋白质拥挤，分布波动和细胞渗透压有关的蛋白质功能方面具有重要意义。在这里，我们报告在压缩力下蛋白质天然结构突然破裂的实验观察结果，通过单分子AFM-FRET光谱纳米技术进行了证明和研究。我们的结果表明，当压缩力达到12–75 pN的阈值时，蛋白质破裂会突然发生，并发生自发事件，可从活细胞中的热波动获得的力幅值。突然破裂对局部环境敏感，这很可能是活细胞中蛋白质展开的一般而重要的途径。