Department of Molecular Biology, Umeå University, Umeå, Sweden.
Department of Biology, Lund University, Lund, Sweden.
Life Sci Alliance. 2019 Jun 26;2(3). doi: 10.26508/lsa.201800290. Print 2019 Jun.
Despite low-sequence homology, the intermediate filament (IF)-like protein FilP from 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.
尽管序列同源性低，但来自 的中间丝 (IF)-样蛋白 FilP 在结构和生化方面与后生动物核 IF 层粘连蛋白相似。FilP 与 IF 蛋白一样，由中央卷曲螺旋结构域组成，中间被短连接子隔开，两端为头部和尾部结构域。FilP 聚合形成具有准晶性质的重复纤维束。然而，发现阳离子 Na 和 K 诱导 FilP 形成六边形网格，其具有与纤维相同的 60nm 重复单元。聚合动力学研究与 EM 技术相结合，使我们能够观察到基本构建块——一种瞬态可溶性棒状 FilP 分子——及其组装成原纤维和纤维束。冷冻电镜断层扫描提供了 FilP 束结构的 3D 视图和原核起源的 IF 样蛋白的原始组装模型，从而能够与后生动物 IF 的组装进行比较。
