title: Structures of the tRNA export factor in the nuclear and cytosolic states.
abstract: Transfer RNAs are among the most ubiquitous molecules in cells, central to decoding information from messenger RNAs on translating ribosomes. In eukaryotic cells, tRNAs are actively transported from their site of synthesis in the nucleus to their site of function in the cytosol. This is mediated by a dedicated nucleo-cytoplasmic transport factor of the karyopherin-beta family (Xpot, also known as Los1 in Saccharomyces cerevisiae). Here we report the 3.2 A resolution structure of Schizosaccharomyces pombe Xpot in complex with tRNA and RanGTP, and the 3.1 A structure of unbound Xpot, revealing both nuclear and cytosolic snapshots of this transport factor. Xpot undergoes a large conformational change on binding cargo, wrapping around the tRNA and, in particular, binding to the tRNA 5' and 3' ends. The binding mode explains how Xpot can recognize all mature tRNAs in the cell and yet distinguish them from those that have not been properly processed, thus coupling tRNA export to quality control.
authors.affiliation: Structural Cell Biology, MPI for Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
authors.forename: Atlanta G
authors.initials: AG
authors.lastname: Cook
authors.forename: Noemi
authors.initials: N
authors.lastname: Fukuhara
authors.forename: Martin
authors.initials: M
authors.lastname: Jinek
authors.forename: Elena
authors.initials: E
authors.lastname: Conti
mesh_terms: D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003600:Cytosol / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D028861:Nuclear Pore Complex Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D034443:RNA Transport; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012360:RNA, Transfer, Phe / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D020931:ran GTP-Binding Protein / Q000737:chemistry / Q000378:metabolism
chemical_list: D020690:GTPase-Activating Proteins; D028861:Nuclear Pore Complex Proteins; D012331:RNA, Fungal; D012360:RNA, Transfer, Phe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C543934:Xpot protein, S pombe; D012343:RNA, Transfer; D020931:ran GTP-Binding Protein
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