Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Soft Matter. 2021 Jan 28;17(4):870-878. doi: 10.1039/d0sm01659d. Epub 2020 Nov 25.
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.
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。丝本身的机械性能编码在其分子结构中，并取决于其离子环境。因此，解开离子类型及其浓度对波形蛋白组装的影响具有重要意义。我们结合小角度 X 射线散射和荧光显微镜，结果表明，在单价离子 K 和 Na 的存在下，波形蛋白组装成“标准丝”，其半径约为 6nm，每个横截面有 32 个单体。相比之下，二价和多价离子，无论类型和价态如何，都会导致更厚的丝形成，这些丝随着时间的推移会结合成更高阶的结构。因此，我们的结果对于活细胞来说确实可能具有相关性，因为在某些生理活动期间细胞质中的局部离子浓度可能与细胞内的平均浓度有很大差异。
