Membrane tension perceived by mechanosensitive (MS) proteins mediates cellular responses to mechanical stimuli and osmotic stresses, and it also guides multiple biological functions including cardiovascular control and development. In bacteria, MS channels function as tension-activated pores limiting excessive turgor pressure, with MscL (MS channel of large conductance) acting as an emergency release valve preventing cell lysis. Previous attempts to simulate gating transitions in MscL by either directly applying steering forces to the protein or by increasing the whole system tension were not fully successful and often disrupted the integrity of the system. We present a novel locally distributed tension molecular dynamics (LDT-MD) simulation method that allows application of forces continuously distributed among lipids surrounding the channel using a specially constructed collective variable. We report reproducible and reversible transitions of MscL to the open state with measured parameters of lateral expansion and conductivity that exactly satisfy experimental values. The LDT-MD method enables exploration of the MscL gating process with different pulling velocities and variable tension asymmetry between the inner and outer membrane leaflets. We use LDT-MD in combination with well-tempered metadynamics to reconstruct the tension-dependent free energy landscape for the opening transition in MscL. The flexible definition of the LDT collective variable allows general application of our method to study mechanical activation of any membrane-embedded protein.

中文翻译：

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局部分布张力分子动力学方法揭示 MscL 的机械活化

机械敏感 (MS) 蛋白感知的膜张力介导细胞对机械刺激和渗透应力的反应，它还指导多种生物学功能，包括心血管控制和发育。在细菌中，MS 通道充当张力激活的孔，限制过度膨胀压力，而 MscL（大电导 MS 通道）充当紧急释放阀，防止细胞裂解。以前通过直接向蛋白质施加转向力或通过增加整个系统张力来模拟 MscL 中的门控转换的尝试并未完全成功，并且经常破坏系统的完整性。我们提出了一种新颖的局部分布张力分子动力学 (LDT-MD) 模拟方法，该方法允许使用特殊构建的集体变量在通道周围的脂质之间连续施加力。我们报告了 MscL 到开放状态的可重复和可逆转变，其中横向膨胀和电导率的测量参数完全满足实验值。LDT-MD 方法能够探索 MscL 门控过程，具有不同的牵引速度和可变的内外膜小叶之间的张力不对称性。我们使用 LDT-MD 结合良好的元动力学来重建 MscL 中开放过渡的张力依赖性自由能景观。