Abstract
The nuclear pore complex (NPC) exhibits structural plasticity and has only been characterized at local resolutions of up to 15 Å for the cytoplasmic ring (CR). Here we present a single-particle cryo-electron microscopy (cryo-EM) structure of the CR from Xenopus laevis NPC at average resolutions of 5.5–7.9 Å, with local resolutions reaching 4.5 Å. Improved resolutions allow identification and placement of secondary structural elements in the majority of the CR components. The two Y complexes in each CR subunit interact with each other and associate with those from flanking subunits, forming a circular scaffold. Within each CR subunit, the Nup358-containing region wraps around the stems of both Y complexes, likely stabilizing the scaffold. Nup205 connects the short arms of the two Y complexes and associates with the stem of a neighboring Y complex. The Nup214-containing region uses an extended coiled-coil to link Nup85 of the two Y complexes and protrudes into the axial pore of the NPC. These previously uncharacterized structural features reveal insights into NPC assembly.
Highlights
The nuclear pore complex (NPC) is the only route of bidirectional cargo transport between the cytoplasm and the nucleus in a eukaryotic cell
Because the nuclear envelope (NE) was planarly spread on the grid, a majority of the NPCs had their cylindrical axes roughly perpendicular to the sample grid, creating an orientation bias
We report the SPAbased cryo-electron microscopy (cryo-electron microscopy (EM)) structure of the entire cytoplasmic ring (CR) subunit at 8.0 Å resolution (Supplementary information, Fig. S3b) and the SPAbase cryo-EM reconstructions of three overlapping regions at average resolutions between 5.5 and 7.9 Å (Fig. 1; Supplementary information, Fig. S4a–c)
Summary
The nuclear pore complex (NPC) is the only route of bidirectional cargo transport between the cytoplasm and the nucleus in a eukaryotic cell. With an estimated molecular mass of about 110–125 MDa in higher eukaryotes, NPC is among the largest and most important cellular machineries.[1,2,3,4,5,6] Detailed structural information is a pre-requisite for mechanistic understanding of NPC function. The cryo-ET reconstruction allows docking of known X-ray structures.[12,13,15,17,18,19]
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