The nuclear pore complex (NPC) mediates the flow of substances between the nucleus and cytoplasm in eukaryotic cells. Here we report the cryo-electron tomography (cryo-ET) structure of the luminal ring (LR) of the NPC from Xenopus laevis oocyte. The observed key structural features of the LR are independently confirmed by single-particle cryo-electron microscopy (cryo-EM) analysis. The LR comprises eight butterfly-shaped subunits, each containing two symmetric wings. Each wing consists of four elongated, tubular protomers. Within the LR subunit, the eight protomers form a Finger domain, which directly contacts the fusion between the inner and outer nuclear membranes and a Grid domain, which serves as a rigid base for the Finger domain. Two neighboring LR subunits interact with each other through the lateral edges of their wings to constitute a Bumper domain, which displays two major conformations and appears to cushion neighboring NPCs. Our study reveals previously unknown features of the LR and potentially explains the elastic property of the NPC.

中文翻译：

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非洲爪蟾核孔复合体腔环的分子结构。


核孔复合体（NPC）介导真核细胞中细胞核和细胞质之间的物质流动。在这里，我们报告了非洲爪蟾卵母细胞 NPC 管腔环 (LR) 的冷冻电子断层扫描 (cryo-ET) 结构。观察到的 LR 的关键结构特征通过单粒子冷冻电子显微镜 (cryo-EM) 分析得到独立证实。 LR 由八个蝴蝶形亚基组成，每个亚基包含两个对称的翅膀。每个翼由四个细长的管状原体组成。在LR亚基内，八个原聚体形成一个Finger结构域，它直接接触内核膜和外核膜之间的融合，以及一个Grid结构域，它作为Finger结构域的刚性基础。两个相邻的 LR 亚基通过其翅膀的侧边缘相互作用，构成一个 Bumper 域，它显示出两种主要构象，似乎可以缓冲相邻的 NPC。我们的研究揭示了 LR 以前未知的特征，并可能解释 NPC 的弹性特性。