Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, 84105, Israel.
Structure. 2012 Jun 6;20(6):998-1006. doi: 10.1016/j.str.2012.03.025. Epub 2012 May 24.
Nuclear pore complexes (NPCs) are the sole passage through the nuclear envelope, connecting the cytoplasm to the nucleoplasm. These gigantic molecular machines, over 100 MDa in molecular weight, allow free diffusion of small molecules and ions while mediating selective energy-dependent nucleocytoplasmic transport of large macromolecules. Here, we applied cryo-electron tomography to human fibroblast cells, reconstructing their nuclear envelopes without applying any purification steps. From these reconstructions, we extracted subtomograms containing individual NPCs and utilized in silico subtomogram averaging procedures to determine the structure of the mammalian pore complex at a resolution of ∼6.6 nm. Beyond revealing the canonical features of the human NPC, our analysis identified inner lateral channels and fusing bridge-like structures, suggesting alternative routes of peripheral nuclear passage. Finally, we concluded from our structural analysis that the human NPC is structurally distinct from that of lower eukaryotes in terms of dimension and organization but resembles its amphibian (frog) counterpart.
核孔复合体（NPC）是核膜上唯一的通道，连接细胞质和核质。这些巨大的分子机器分子量超过 100MDa，允许小分子和离子自由扩散，同时介导大分子的选择性、能量依赖的核质转运。在这里，我们应用冷冻电子断层扫描技术对人成纤维细胞进行研究，在不进行任何纯化步骤的情况下重建其核膜。从这些重建中，我们提取了包含单个 NPC 的亚断层图像，并利用计算机亚断层平均程序确定了哺乳动物核孔复合体的结构，分辨率约为 6.6nm。除了揭示了人类 NPC 的典型特征外，我们的分析还确定了内部横向通道和融合桥状结构，表明了核周的替代通道。最后，我们从结构分析中得出结论，人类 NPC 在尺寸和组织上与低等真核生物的 NPC 结构不同，但与两栖动物（青蛙）的 NPC 相似。
