title: Karyopherin-independent spontaneous transport of amphiphilic proteins through the nuclear pore.
abstract: Highly selective nucleocytoplasmic molecular transport is critical to eukaryotic cells, which is illustrated by size-filtering diffusion and karyopherin-mediated passage mechanisms. However, a considerable number of large proteins without nuclear localization signals are localized to the nucleus. In this paper, we provide evidence for the spontaneous migration of large proteins in a karyopherin-independent manner. Time-lapse observation of a nuclear transport assay revealed that several large molecules spontaneously and independently pass through the nuclear pore complex (NPC). The amphiphilic motifs were sufficient to overcome the selectivity barrier of the NPC. Furthermore, the amphiphilic property of these proteins enables altered local conformation in hydrophobic solutions so that elevated surface hydrophobicity facilitates passage through the nuclear pore. The molecular dynamics simulation revealed the conformational change of the amphiphilic structure that exposes the hydrophobic amino acid residues to the outer surface in a hydrophobic solution. These results contribute to the understanding of nucleocytoplasmic molecular sorting and the nature of the permeability barrier.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan. kumeta@lif.kyoto-u.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kumeta
authors.forename: Hideki
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Shige H
authors.initials: SH
authors.lastname: Yoshimura
authors.forename: Kunio
authors.initials: K
authors.lastname: Takeyasu
mesh_terms: D000185:Actinin / Q000737:chemistry / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D028884:Karyopherins / Q000502:physiology*; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D022022:Nuclear Pore / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D061987:Sf9 Cells; D013049:Spectrin / Q000737:chemistry / Q000378:metabolism; D018411:Spodoptera; D013499:Surface Properties; D059008:Time-Lapse Imaging; D051176:beta Catenin / Q000737:chemistry / Q000378:metabolism
chemical_list: C111453:ACTN4 protein, human; D028884:Karyopherins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D051176:beta Catenin; D000185:Actinin; D013049:Spectrin; D049452:Green Fluorescent Proteins