Despite low-sequence homology, the intermediate filament (IF)-like protein FilP from Streptomyces coelicolor displays structural and biochemical similarities to the metazoan nuclear IF lamin. FilP, like IF proteins, is composed of central coiled-coil domains interrupted by short linkers and flanked by head and tail domains. FilP polymerizes into repetitive filament bundles with paracrystalline properties. However, the cations Na⁺ and K⁺ are found to induce the formation of a FilP hexagonal meshwork with the same 60-nm repetitive unit as the filaments. Studies of polymerization kinetics, in combination with EM techniques, enabled visualization of the basic building block-a transiently soluble rod-shaped FilP molecule-and its assembly into protofilaments and filament bundles. Cryoelectron tomography provided a 3D view of the FilP bundle structure and an original assembly model of an IF-like protein of prokaryotic origin, thereby enabling a comparison with the assembly of metazoan IF.

中文翻译：

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细菌细胞骨架蛋白FilP的组装机制。

尽管序列同源性很低，但来自天蓝色链霉菌的中间丝（IF）样蛋白FilP与后生动物核IF层粘蛋白显示出结构和生化相似性。像IF蛋白一样，FilP由中央卷曲螺旋结构域组成，该结构域被短连接子打断，并在头和尾结构域的两侧。FilP聚合成具有顺晶特性的重复长丝束。但是，阳离子Na ⁺和K ⁺被发现可以诱导形成具有与细丝相同的60 nm重复单元的FilP六角网状结构。聚合动力学的研究与EM技术相结合，使可视化的基本结构单元-瞬时可溶的棒状FilP分子-并组装成原丝和长丝束。低温电子断层扫描提供了FilP束结构的3D视图以及原核起源的IF样蛋白的原始装配模型，从而能够与后生动物IF的装配进行比较。