2x19 | pdb_00002x19
CRYSTAL STRUCTURE OF IMPORTIN13 - RANGTP COMPLEX
Structural highlights
Function[GSP1_YEAST] GTP-binding protein involved in nucleocytoplasmic transport. Required for the import of protein into the nucleus and also for RNA export. Essential for cell viability. By analogy with Ras, Ran may be activated when GTP is exchanged for bound GDP by RCC1 and inactivated when GTP is hydrolyzed by Ran upon activation by RanGAP1. [IPO13_HUMAN] Functions in nuclear protein import as nuclear transport receptor. Serves as receptor for nuclear localization signals (NLS) in cargo substrates. Is thought to mediate docking of the importin/substrate complex to the nuclear pore complex (NPC) through binding to nucleoporin and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to the importin, the importin/substrate complex dissociates and importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus (By similarity). Mediates the nuclear import of UBC9, the RBM8A/MAGOH complex, PAX6 and probably other members of the paired homeobox family. Also mediates nuclear export of eIF-1A, and the cytoplasmic release of eIF-1A is triggered by the loading of import substrates onto IPO13.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMago and Y14 are core components of the exon junction complex (EJC), an assembly central to nonsense-mediated mRNA decay in humans and mRNA localization in flies. The Mago-Y14 heterodimer shuttles between the nucleus, where it is loaded onto specific mRNAs, and the cytoplasm, where it functions in translational regulation. The heterodimer is imported back into the nucleus by Importin 13 (Imp13), a member of the karyopherin-beta family of transport factors. We have elucidated the structural basis of the Mago-Y14 nuclear import cycle. The 3.35 A structure of the Drosophila Imp13-Mago-Y14 complex shows that Imp13 forms a ring-like molecule, reminiscent of Crm1, and encircles the Mago-Y14 cargo with a conserved interaction surface. The 2.8 A structure of human Imp13 bound to RanGTP reveals how Mago-Y14 is released in the nucleus by a steric hindrance mechanism. Comparison of the two structures suggests how this unusual karyopherin might function in bidirectional nucleocytoplasmic transport. Nuclear import mechanism of the EJC component Mago-Y14 revealed by structural studies of importin 13.,Bono F, Cook AG, Grunwald M, Ebert J, Conti E Mol Cell. 2010 Jan 29;37(2):211-22. PMID:20122403[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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