Transport receptor occupancy in nuclear pore complex mimics

Abstract Nuclear pore complexes (NPCs) regulate all molecular transport between the nucleus and cytoplasm in eukaryotic cells. Intrinsically disordered Phe-Gly nucleoporins (FG-Nups) line central conduit of NPCs to impart a selective barrier where large proteins are excluded unless bound receptor (karyopherin; Kap). Here, we assess “Kap-centric” NPC models, which postulate that Kaps participate establishing barrier. We combine biomimetic nanopores, formed by tethering Nsp1 inner wall solid-state nanopore, with coarse-grained modeling show yeast Kap95 exhibits two populations Nsp1-coated pores: one population is transported across milliseconds, second stably assembled within FG mesh pore. Ionic current measurements conductance decrease for increasing Kap concentrations noise data indicate an increase rigidity FG-mesh. Modeling reveals accumulation near wall, yielding decrease. find only mildly affect conformation that, even at high concentrations, bind most 8% FG-motifs indicating occupancy limited steric constraints rather than depletion available FG-motifs. Our provide alternative explanation origin bimodal binding Kaps, stable binds avidly periphery, while fast proceeds via FG-rich channel through lower affinity interactions cohesive domains Nsp1.