Hémonnot Clément Y J, Mauermann Monika, Herrmann Harald, Köster Sarah
Institute for X-ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Division of Molecular Genetics, German Cancer Research Center , Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Biomacromolecules. 2015 Oct 12;16(10):3313-21. doi: 10.1021/acs.biomac.5b00965. Epub 2015 Sep 11.
The intermediate filament proteins keratin K8 and K18 constitute an essential part of the cytoskeleton in simple epithelial cell layers, structurally enforcing their mechanical resistance. K8/K18 heterodimers form extended filaments and higher-order structures including bundles and networks that bind to cell junctions. We study the assembly of these proteins in the presence of monovalent or divalent ions by small-angle X-ray scattering. We find that both ion species cause an increase of the filament diameter when their concentration is increased; albeit, much higher values are needed for the monovalent compared to the divalent ions for the same effect. Bundling occurs also for monovalent ions and at comparatively low concentrations of divalent ions, very different from vimentin intermediate filaments, a fibroblast-specific cytoskeleton component. We explain these differences by variations in charge and hydrophobicity patterns of the proteins. These differences may reflect the respective physiological situation in stationary cell layers versus single migrating fibroblasts.
中间丝蛋白角蛋白K8和K18构成简单上皮细胞层细胞骨架的重要组成部分，在结构上增强其机械抗性。K8/K18异二聚体形成延伸的细丝以及包括束和网络在内的高阶结构，这些结构与细胞连接结合。我们通过小角X射线散射研究这些蛋白质在单价或二价离子存在下的组装情况。我们发现，当单价或二价离子浓度增加时，细丝直径都会增大；尽管如此，对于相同的效果，单价离子所需的浓度比二价离子高得多。单价离子也会发生成束现象，并且在相对较低浓度的二价离子下也会发生，这与波形蛋白中间丝（一种成纤维细胞特异性细胞骨架成分）非常不同。我们通过蛋白质电荷和疏水性模式的变化来解释这些差异。这些差异可能反映了静止细胞层与单个迁移成纤维细胞各自的生理状况。
