title: Separate binding sites on nuclear transport factor 2 (NTF2) for GDP-Ran and the phenylalanine-rich repeat regions of nucleoporins p62 and Nsp1p.
abstract: Nuclear transport factor 2 (NTF2) facilitates nuclear protein import through nuclear pore complexes (NPCs). Bacterially expressed rat NTF2 exists in solution as dimers and, when bound to Sepharose beads, is able to interact specifically with both the Ras-like GTPase Ran, and the xFxFG repeat containing domains of nucleoporins p62 (vertebrate) and Nsp1p (yeast). These interactions are sufficiently strong and specific to enable native Ran and p62 to be isolated from crude rat liver homogenates. Comparison of the sequences of the xFxFG repeat regions of p62 and Nsplp indicated that NTF2 was probably interacting with the phenylalanine-containing core of these repeats and not the intervening hydrophilic linkers. Ran and p62 do not compete with one another for binding to NTF2, indicating that they bind to different sites on NTF2. These interactions could help target Ran and NTF2 to a series of putative docking sites for the importin-substrate complex located along the central transport channel of the NPC and so facilitate the passage of import material being transported from the cytoplasm into the nucleus.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, England.
authors.forename: W D
authors.initials: WD
authors.lastname: Clarkson
authors.forename: H M
authors.initials: HM
authors.lastname: Kent
authors.forename: M
authors.initials: M
authors.lastname: Stewart
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002853:Chromatography, Liquid / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005656:Fungal Proteins / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D010649:Phenylalanine / Q000737:chemistry; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D029701:Saccharomyces cerevisiae Proteins; D012685:Sepharose; D012710:Serum Albumin, Bovine / Q000378:metabolism; D020931:ran GTP-Binding Protein
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; C062748:NSP1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C503612:Nutf2 protein, rat; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C049312:nuclear pore protein p62; D006153:Guanosine Diphosphate; D012710:Serum Albumin, Bovine; D010649:Phenylalanine; D012685:Sepharose; D020931:ran GTP-Binding Protein