title: Structural basis for the assembly of a nuclear export complex.
abstract: The nuclear import and export of macromolecular cargoes through nuclear pore complexes is mediated primarily by carriers such as importin-beta. Importins carry cargoes into the nucleus, whereas exportins carry cargoes to the cytoplasm. Transport is orchestrated by nuclear RanGTP, which dissociates cargoes from importins, but conversely is required for cargo binding to exportins. Here we present the 2.0 A crystal structure of the nuclear export complex formed by exportin Cse1p complexed with its cargo (Kap60p) and RanGTP, thereby providing a structural framework for understanding nuclear protein export and the different functions of RanGTP in export and import. In the complex, Cse1p coils around both RanGTP and Kap60p, stabilizing the RanGTP-state and clamping the Kap60p importin-beta-binding domain, ensuring that only cargo-free Kap60p is exported. Mutagenesis indicated that conformational changes in exportins couple cargo binding to high affinity for RanGTP, generating a spring-loaded molecule to facilitate disassembly of the export complex following GTP hydrolysis in the cytoplasm.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Murray
authors.initials: M
authors.lastname: Stewart
mesh_terms: D021581:Active Transport, Cell Nucleus; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D046912:Multiprotein Complexes; D022022:Nuclear Pore / Q000737:chemistry* / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000737:chemistry* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D020931:ran GTP-Binding Protein / Q000737:chemistry / Q000378:metabolism
chemical_list: C082274:CSE1 protein, S cerevisiae; D046912:Multiprotein Complexes; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D006160:Guanosine Triphosphate; D020931:ran GTP-Binding Protein