Vimentin intermediate filaments, together with actin filaments and microtubules, constitute the cytoskeleton in cells of mesenchymal origin. The mechanical properties of the filaments themselves are encoded in their molecular architecture and depend on their ionic environment. It is thus of great interest to disentangle the influence of both the ion type and their concentration on vimentin assembly. We combine small angle X-ray scattering and fluorescence microscopy and show that vimentin in the presence of the monovalent ions, K⁺ and Na⁺, assembles into “standard filaments” with a radius of about 6 nm and 32 monomers per cross-section. In contrast, di- and multivalent ions, independent of type and valency, lead to the formation of thicker filaments associating over time into higher order structures. Hence, our results may indeed be of relevance for living cells, as local ion concentrations in the cytoplasm during certain physiological activities may differ considerably from average intracellular concentrations.

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离子类型和价不同地驱动波形蛋白四聚体进入中间丝或更高阶的组件

波形蛋白中间丝与肌动蛋白丝和微管一起构成了间充质来源细胞的细胞骨架。长丝本身的机械性能在其分子结构中编码，并取决于其离子环境。因此，非常有趣的是弄清离子类型及其浓度对波形蛋白组装的影响。我们将小角度X射线散射和荧光显微镜相结合，表明波形蛋白在单价离子K ⁺和Na ^+存在下组装成半径约6 nm的“标准细丝”，每个横截面包含32个单体。相反，二价和多价离子与类型和化合价无关，会导致形成较粗的细丝，这些细丝会随着时间的流逝而缔合成更高阶的结构。因此，我们的结果可能确实与活细胞有关，因为在某些生理活动中细胞质中的局部离子浓度可能与平均细胞内浓度相差很大。