M.M. Shemyakin & Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, Moscow, 117997, Russia.
Scientific and Research Center "BioClinicum", Ugreshkaya Street, 2/85, Moscow, 115088, Russia.
Sci Rep. 2019 Jan 23;9(1):413. doi: 10.1038/s41598-018-36310-6.
How is a water-soluble globular protein able to spontaneously cross a cellular membrane? It is commonly accepted that it undergoes significant structural rearrangements on the lipid-water interface, thus acquiring membrane binding and penetration ability. In this study molecular dynamics (MD) simulations have been used to explore large-scale conformational changes of the globular viscumin A chain in a complex environment - comprising urea and chloroform/methanol (CHCl/MeOH) mixture. Being well-packed in aqueous solution, viscumin A undergoes global structural rearrangements in both organic media. In urea, the protein is "swelling" and gradually loses its long-distance contacts, thus resembling the "molten globule" state. In CHCl/MeOH, viscumin A is in effect turned "inside out". This is accompanied with strengthening of the secondary structure and surface exposure of hydrophobic epitopes originally buried inside the globule. Resulting solvent-adapted models were further subjected to Monte Carlo simulations with an implicit hydrophobic slab membrane. In contrast to only a few point surface contacts in water and two short regions with weak protein-lipid interactions in urea, MD-derived structures in CHCl/MeOH reveal multiple determinants of membrane interaction. Consequently it is now possible to propose a specific pathway for the structural adaptation of viscumin A with respect to the cell membrane - a probable first step of its translocation into cytoplasmic targets.
一种水溶性球状蛋白质如何能够自发地穿过细胞膜？人们普遍认为，它在脂质-水界面上经历了显著的结构重排，从而获得了膜结合和穿透能力。在这项研究中，使用分子动力学（MD）模拟来探索球状 viscumin A 链在复杂环境中的大规模构象变化 - 包括尿素和氯仿/甲醇（CHCl/MeOH）混合物。在水溶液中良好堆积的 viscumin A 在两种有机介质中都经历了全局结构重排。在尿素中，蛋白质“肿胀”并逐渐失去长程接触，从而类似于“熔融球蛋白”状态。在 CHCl/MeOH 中，viscumin A 实际上是“里外翻转”。这伴随着二级结构的增强和原本埋藏在球蛋白内部的疏水表位的暴露。由此产生的溶剂适应模型进一步用隐式疏水平板膜进行了蒙特卡罗模拟。与仅在水中有几个点的表面接触和尿素中只有两个弱蛋白-脂质相互作用的短区域相比，CHCl/MeOH 中的 MD 衍生结构揭示了与膜相互作用的多个决定因素。因此，现在可以提出 viscumin A 与细胞膜结构适应的具体途径 - 这可能是其进入细胞质靶标的第一步。
