Native Cellular Membranes Facilitate Channel Activity of MscL by Enhancing Slow Collective Motions of Its Transmembrane Helices

Mechanosensitive channels of large conductance (MscL) serve as a mechanoelectrical valve of cells in response to membrane tension. The influence of membrane environments to MscL channel activity and the underlying mechanism remains unclear. Herein, we developed a new sample preparation protocol that allows for the detection of high-quality 1H-detected solid-state NMR spectra of MscL in cellular membranes, enabling site-specific analysis of its dynamics. Dipolar order parameters and spin relaxation rates are measured for 51 residues of MscL in synthetic and native membrane. The dynamics data reveal that while MscL maintains a similar rigidity in both membrane environments, it exhibits enhanced slow collective motions in the native cellular membranes. Molecular dynamics simulations demonstrate the critical role of slow motions in the mechanosensitivity of MscL by promoting protein-membrane interactions. This study examines atomic-resolution dynamics of a membrane-protein in cellular membranes and provides novel insights into functional significance of membrane-protein dynamics.

大电导机械敏感离子通道（Mechanosensitive channels of large conductance, MscL）是响应膜张力的细胞机械电阀门。目前，膜环境对MscL通道活性的影响及其潜在分子机制仍不明确。本研究开发了一种全新的样品制备方案，可实现细胞膜中MscL的高质量氢检测固态核磁共振（solid-state NMR）波谱采集，从而能够对其动力学特性开展位点特异性分析。研究人员在合成膜与天然细胞膜中，对MscL的51个残基的偶极序参数与自旋弛豫速率进行了测定。动力学数据分析结果显示，尽管MscL在两种膜环境中均保持相近的刚性，但在天然细胞膜中展现出更强的慢速集体运动特性。分子动力学模拟结果表明，慢速运动可通过促进蛋白-膜相互作用，在MscL的机械敏感性中发挥关键作用。本研究针对细胞膜环境中的膜蛋白开展了原子分辨率动力学分析，为阐明膜蛋白动力学的功能意义提供了全新的研究视角。