Abstract
Nuclear pore complexes (NPCs) perforate the nuclear envelope and allow the exchange of macromolecules between the nucleus and the cytoplasm. To acquire a deeper understanding of this transport mechanism, we analyse the structure of the NPC scaffold and permeability barrier, by reconstructing the Xenopus laevis oocyte NPC from native nuclear envelopes up to 20 Å resolution by cryo-electron tomography in conjunction with subtomogram averaging. In addition to resolving individual protein domains of the NPC constituents, we propose a model for the architecture of the molecular gate at its central channel. Furthermore, we compare and contrast this native NPC structure to one that exhibits reduced transport activity and unveil the spatial properties of the NPC gate.
Highlights
Nuclear pore complexes (NPCs) perforate the nuclear envelope and allow the exchange of macromolecules between the nucleus and the cytoplasm
The a-solenoid/b-propeller containing Nups, for example, are mostly scaffold elements, the transmembrane Nups anchor the NPCs to the nuclear envelope (NE), while phenylalanine–glycine (FG) repeat containing Nups interact with cargo–receptor complexes[7] and constitute the permeability barrier of the central channel[20]
By employing an improved structural analysis of the X. laevis NPC in different states of transport, we show that these structures assemble to form a molecular gate at the central channel of the NPC
Summary
Nuclear pore complexes (NPCs) perforate the nuclear envelope and allow the exchange of macromolecules between the nucleus and the cytoplasm. Nuclear pore complexes (NPCs) mediate the macromolecular exchange between the nucleoplasm and cytoplasm[1,2] These supramolecular assemblies, 60–125 MDa in molecular weight[3,4], constitute the sole gateway through the nuclear envelope (NE). Individual Y-shaped complexes interact in a head-to-tail fashion to form ring-like octameric entities[13,16,17], that are integral part of the scaffold[14] This complex plays a pivotal role in NPC assembly and its absence results in pore-free nuclei with a continuous NE, as shown in studies of depleted Xenopus laevis egg extracts[18,19]. Acquiring high-resolution structural data on the conformation and gating properties of FG Nups within the confined and crowded central channel is crucial for a deeper understanding of nuclear transport. By employing an improved structural analysis of the X. laevis NPC in different states of transport, we show that these structures assemble to form a molecular gate at the central channel of the NPC
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