Department of Cellular Logistics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
Quantitative Biology, IRI Life Sciences, Humboldt-Universität zu Berlin, Berlin, Germany.
Nat Commun. 2023 Feb 10;14(1):747. doi: 10.1038/s41467-023-36331-4.
Nup98 FG repeat domains comprise hydrophobic FG motifs linked through uncharged spacers. FG motifs capture nuclear transport receptors (NTRs) during nuclear pore complex (NPC) passage, confer inter-repeat cohesion, and condense the domains into a selective phase with NPC-typical barrier properties. We show that shortening inter-FG spacers enhances cohesion, increases phase density, and tightens such barrier - all consistent with a sieve-like phase. Phase separation tolerates mutating the Nup98-typical GLFG motifs, provided domain-hydrophobicity remains preserved. NTR-entry, however, is sensitive to (certain) deviations from canonical FG motifs, suggesting co-evolutionary adaptation. Unexpectedly, we observed that arginines promote FG-phase-entry apparently also by hydrophobic interactions/ hydrogen-bonding and not just through cation-π interactions. Although incompatible with NTR·cargo complexes, a YG phase displays remarkable transport selectivity, particularly for engineered GFP-variants. GLFG to FSFG mutations make the FG phase hypercohesive, precluding NTR-entry. Extending spacers relaxes this hypercohesion. Thus, antagonism between cohesion and NTR·FG interactions is key to transport selectivity.
Nup98 FG 重复结构域由通过不带电间隔物连接的疏水性 FG 基序组成。FG 基序在核孔复合体 (NPC) 穿过时捕获核转运受体 (NTR)，赋予重复结构域之间的内聚性，并将结构域浓缩成具有 NPC 典型屏障特性的选择性相。我们表明，缩短 FG 间隔物会增强内聚性，增加相密度，并使这种屏障更加紧密 - 所有这些都与筛状相一致。相分离可以容忍突变 Nup98 典型的 GLFG 基序，只要保留结构域的疏水性。然而，NTR 进入对（某些）偏离典型 FG 基序非常敏感，这表明存在共同进化的适应性。出乎意料的是，我们观察到精氨酸通过疏水性相互作用/氢键，而不仅仅是通过阳离子-π 相互作用，促进 FG 相进入。尽管与 NTR·货物复合物不兼容，但 YG 相表现出显著的运输选择性，特别是对于工程 GFP 变体。GLFG 到 FSFG 的突变使 FG 相超凝聚，阻止 NTR 进入。延长间隔物会减轻这种超凝聚性。因此，内聚性和 NTR·FG 相互作用之间的拮抗作用是运输选择性的关键。
