title: Nanoscale mechanism of molecular transport through the nuclear pore complex as studied by scanning electrochemical microscopy.
abstract: The nuclear pore complex (NPC) is the proteinaceous nanopore that solely mediates molecular transport across the nuclear envelope between the nucleus and cytoplasm of a eukaryotic cell. Small molecules (<40 kDa) diffuse through the large pore of this multiprotein complex. A passively impermeable macromolecule tagged with a signal peptide is chaperoned through the nanopore by nuclear transport receptors (e.g., importins) owing to their interactions with barrier-forming proteins. Presently, this bimodal transport mechanism is not well understood and is described by controversial models. Herein, we report on a dynamic and spatially resolved mechanism for NPC-mediated molecular transport through nanoscale central and peripheral routes with distinct permeabilities. Specifically, we develop a nanogap-based approach of scanning electrochemical microscopy to precisely measure the extremely high permeability of the nuclear envelope to a small probe molecule, (ferrocenylmethyl)trimethylammonium. Effective medium theories indicate that the passive permeability of 5.9 × 10(-2) cm/s corresponds to the free diffusion of the probe molecule through ~22 nanopores with a radius of 24 nm and a length of 35 nm. Peripheral routes are blocked by wheat germ agglutinin to yield 2-fold lower permeability for 17 nm-radius central routes. This lectin is also used in fluorescence assays to find that importins facilitate the transport of signal-tagged albumin mainly through the 7 nm-thick peripheral route rather than through the sufficiently large central route. We propose that this spatial selectivity is regulated by the conformational changes in barrier-forming proteins that transiently and locally expand the impermeably thin peripheral route while blocking the central route.
authors: Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA.
authors: Jiyeon
authors: J
authors: Kim
authors: Anahita
authors: A
authors: Izadyar
authors: Nikoloz
authors: N
authors: Nioradze
authors: Shigeru
authors: S
authors: Amemiya
mesh_terms: D028884:Karyopherins / Q000737:chemistry / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures / Q000737:chemistry*; D022022:Nuclear Pore / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D028884:Karyopherins; D010455:Peptides