Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness
Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness
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DOI：
10.1073/pnas.1211078109
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发表时间：
2012-10-16
影响因子：
11.1
通讯作者：
De La Cruz, Enrique M.
中科院分区：
文献类型：
--
作者：
Kang, Hyeran;Bradley, Michael J.;De La Cruz, Enrique M.
肌动蛋白单体组装成细丝和网络在真核生物中起着至关重要的作用，包括细胞内运输、细胞运动、细胞分裂、决定细胞形状和提供细胞机械强度。肌动蛋白组装的调节和纤维力学性能的调节是肌动蛋白正常工作的关键。生理盐浓度促进肌动蛋白组装并改变组装的细丝和网络的整体弯曲力学。然而，这些盐依赖效应的分子起源，特别是如果它们涉及非特异性离子强度效应或特异性离子结合相互作用，是未知的。在这里，我们证明了位于相邻亚基之间的两个离散位点的特定阳离子结合沿着长螺距螺旋驱动肌动蛋白聚合，并决定了丝的弯曲刚度。我们将这两个位点分别分类为“聚合”位点和“刚度”位点，这是基于位点突变对盐依赖性纤维组装和弯曲力学的影响。这些结果确定了阳离子结合位点的存在和位置，使肌动蛋白丝的组装和力学依赖于盐。
The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as "polymerization" and "stiffness" sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments.