Schmidt Hermann Broder, Görlich Dirk
Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Elife. 2015 Jan 6;4:e04251. doi: 10.7554/eLife.04251.
Nuclear pore complexes (NPCs) conduct massive transport mediated by shuttling nuclear transport receptors (NTRs), while keeping nuclear and cytoplasmic contents separated. The NPC barrier in Xenopus relies primarily on the intrinsically disordered FG domain of Nup98. We now observed that Nup98 FG domains of mammals, lancelets, insects, nematodes, fungi, plants, amoebas, ciliates, and excavates spontaneously and rapidly phase-separate from dilute (submicromolar) aqueous solutions into characteristic 'FG particles'. This required neither sophisticated experimental conditions nor auxiliary eukaryotic factors. Instead, it occurred already during FG domain expression in bacteria. All Nup98 FG phases rejected inert macromolecules and yet allowed far larger NTR cargo complexes to rapidly enter. They even recapitulated the observations that large cargo-domains counteract NPC passage of NTR⋅cargo complexes, while cargo shielding and increased NTR⋅cargo surface-ratios override this inhibition. Their exquisite NPC-typical sorting selectivity and strong intrinsic assembly propensity suggest that Nup98 FG phases can form in authentic NPCs and indeed account for the permeability properties of the pore.
核孔复合体（NPCs）介导由穿梭核转运受体（NTRs）进行的大量运输，同时保持细胞核和细胞质内容物的分离。非洲爪蟾中的NPC屏障主要依赖于核孔蛋白98（Nup98）的内在无序FG结构域。我们现在观察到，哺乳动物、文昌鱼、昆虫、线虫、真菌、植物、变形虫、纤毛虫和挖掘类生物的Nup98 FG结构域会自发且迅速地从稀（亚微摩尔）水溶液中相分离成特征性的“FG颗粒”。这既不需要复杂的实验条件，也不需要辅助真核因子。相反，它在细菌中FG结构域表达期间就已发生。所有Nup98 FG相都排斥惰性大分子，但允许大得多的NTR货物复合体迅速进入。它们甚至重现了以下观察结果：大的货物结构域会阻碍NTR·货物复合体通过NPC，而货物屏蔽和增加的NTR·货物表面比率会克服这种抑制作用。它们精细的NPC典型分选选择性和强大的内在组装倾向表明，Nup98 FG相可以在真实的NPC中形成，并且确实决定了核孔的通透性特性。
