NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States.
Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States.
J Phys Chem B. 2018 Apr 12;122(14):3826-3835. doi: 10.1021/acs.jpcb.8b00663. Epub 2018 Apr 2.
Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.
肌动蛋白纤维束是细胞骨架力学支撑和动态重组的关键因素。多价抗衡离子的高浓度通过带负电荷的聚电解质肌动蛋白纤维之间的静电吸引促进纤维束的形成。在这项研究中，我们评估了生理相关的二价阳离子如何影响肌动蛋白纤维束的力学、动态和结构特性。我们使用全内反射荧光显微镜、透射电子显微镜和动态光散射的组合，证明了二价阳离子调节纤维束的硬度、长度分布和侧向生长。肌动蛋白纤维束的全原子模型的分子动力学模拟揭示了特定的肌动蛋白残基协调阳离子结合位点，促进了纤维束的形成。我们的工作表明，特定的阳离子相互作用可能在肌动蛋白纤维束的组装、结构和力学性质中起基础性作用。
