Near atomic structure of the inner ring of the Saccharomyces cerevisiae nuclear pore complex

Nuclear pore complexes (NPCs) mediate bidirectional nucleocytoplasmic transport of substances in eukaryotic cells. However, the accurate molecular arrangement of NPCs remains enigmatic owing to their huge size and highly dynamic nature. Here we determined the structure of the asymmetric unit of the inner ring (IR monomer) at 3.73 [A] resolution by single-particle cryo-electron microscopy, and created an atomic model of the intact IR consisting of 192 copies from 8 subunits. In each IR monomer, two approximately parallel rhomboidal structures of the inner and outer layers are sandwiched with the Z-shaped Nup188-Nup192 middle layer and Nup188, Nup192 and Nic96 link all subunits to constitute a relatively stable IR monomer, while the intact IR is assembled by loose and instable interactions between IR monomer. These structures reveal various interaction modes and extensive flexible connections in the assembly, providing a structural basis for the stability and malleability of IR. One-Sentence SummaryAccurate structure of inner ring reveals its assembly and function in dilation and constriction of nuclear pore complex.