Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California 90095, USA.
Electron Imaging Center for Nanomachines, California Nano Systems Institute, UCLA, Los Angeles (UCLA), Los Angeles, California 90095, USA.
Nat Microbiol. 2016 Dec 5;2:16222. doi: 10.1038/nmicrobiol.2016.222.
Archaea use flagella known as archaella-distinct both in protein composition and structure from bacterial flagella-to drive cell motility, but the structural basis of this function is unknown. Here, we report an atomic model of the archaella, based on the cryo electron microscopy (cryoEM) structure of the Methanospirillum hungatei archaellum at 3.4 Å resolution. Each archaellum contains ∼61,500 archaellin subunits organized into a curved helix with a diameter of 10 nm and average length of 10,000 nm. The tadpole-shaped archaellin monomer has two domains, a β-barrel domain and a long, mildly kinked α-helix tail. Our structure reveals multiple post-translational modifications to the archaella, including six O-linked glycans and an unusual N-linked modification. The extensive interactions among neighbouring archaellins explain how the long but thin archaellum maintains the structural integrity required for motility-driving rotation. These extensive inter-subunit interactions and the absence of a central pore in the archaellum distinguish it from both the bacterial flagellum and type IV pili.
古菌使用鞭毛，称为 archaea，其蛋白质组成和结构与细菌鞭毛明显不同，用于驱动细胞运动，但这种功能的结构基础尚不清楚。在这里，我们基于 3.4 Å 分辨率的 Methanospirillum hungatei archaea 冷冻电子显微镜 (cryoEM) 结构，报告了 archaea 的原子模型。每个 archaea 包含约 61500 个 archaealin 亚基，组织成一个直径为 10nm、平均长度为 10000nm 的弯曲螺旋。蝌蚪形 archaealin 单体有两个结构域，一个β桶结构域和一个长而轻度弯曲的α螺旋尾巴。我们的结构揭示了 archaea 的多种翻译后修饰，包括六个 O-连接聚糖和一种不寻常的 N-连接修饰。相邻 archaealin 之间的广泛相互作用解释了长而细的 archaea 如何保持运动驱动旋转所需的结构完整性。这种广泛的亚基间相互作用以及 archaea 中没有中心孔将其与细菌鞭毛和 IV 型菌毛区分开来。
