| Structural highlights
Function
[TNPO1_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). Involved in nuclear import of M9-containing proteins. In vitro, binds directly to the M9 region of the heterogeneous nuclear ribonucleoproteins (hnRNP), A1 and A2 and mediates their nuclear import. Appears also to be involved in hnRNP A1/A2 nuclear export. Mediates the nuclear import of ribosomal proteins RPL23A, RPS7 and RPL5. Binds to a beta-like import receptor binding (BIB) domain of RPL23A. In vitro, mediates nuclear import of H2A, H2B, H3 and H4 histones, and SRP19. In case of HIV-1 infection, binds and mediates the nuclear import of HIV-1 Rev. Mediates nuclear import of ADAR/ADAR1 (isoform 5) in a RanGTP-dependent manner.[1] [2] [3] [4] [RAN_HUMAN] GTP-binding protein involved in nucleocytoplasmic transport. Required for the import of protein into the nucleus and also for RNA export. Involved in chromatin condensation and control of cell cycle (By similarity). The complex with BIRC5/ survivin plays a role in mitotic spindle formation by serving as a physical scaffold to help deliver the RAN effector molecule TPX2 to microtubules. Acts as a negative regulator of the kinase activity of VRK1 and VRK2.[5] [6] [7] [8] Enhances AR-mediated transactivation. Transactivation decreases as the poly-Gln length within AR increases.[9] [10] [11] [12]
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 PubMed
Transport factors in the karyopherin-beta (also called importin-beta) family mediate the movement of macromolecules in nuclear-cytoplasmic transport pathways. Karyopherin-beta2 (transportin) binds a cognate import substrate and targets it to the nuclear pore complex. In the nucleus, Ran x GTP binds karyopherin-beta2 and dissociates the substrate. Here we present the 3.0 A structure of the karyopherin-beta2-Ran x GppNHp complex where GppNHp is a non-hydrolysable GTP analogue. Karyopherin-beta2 contains eighteen HEAT repeats arranged into two continuous orthogonal arches. Ran is clamped in the amino-terminal arch and substrate-binding activity is mapped to the carboxy-terminal arch. A large loop in HEAT repeat 7 spans both arches. Interactions of the loop with Ran and the C-terminal arch implicate it in GTPase-mediated dissociation of the import-substrate. Ran x GppNHp in the complex shows extensive structural rearrangement, compared to Ran GDP, in regions contacting karyopherin-beta2. This provides a structural basis for the specificity of the karyopherin-beta family for the GTP-bound state of Ran, as well as a rationale for interactions of the karyopherin-Ran complex with the regulatory proteins ranGAP, ranGEF and ranBP1.
Structure of the nuclear transport complex karyopherin-beta2-Ran x GppNHp.,Chook YM, Blobel G Nature. 1999 May 20;399(6733):230-7. PMID:10353245[13]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Nakielny S, Siomi MC, Siomi H, Michael WM, Pollard V, Dreyfuss G. Transportin: nuclear transport receptor of a novel nuclear protein import pathway. Exp Cell Res. 1996 Dec 15;229(2):261-6. PMID:8986607 doi:10.1006/excr.1996.0369
- ↑ Jakel S, Gorlich D. Importin beta, transportin, RanBP5 and RanBP7 mediate nuclear import of ribosomal proteins in mammalian cells. EMBO J. 1998 Aug 3;17(15):4491-502. PMID:9687515 doi:10.1093/emboj/17.15.4491
- ↑ Dean KA, von Ahsen O, Gorlich D, Fried HM. Signal recognition particle protein 19 is imported into the nucleus by importin 8 (RanBP8) and transportin. J Cell Sci. 2001 Oct;114(Pt 19):3479-85. PMID:11682607
- ↑ Fritz J, Strehblow A, Taschner A, Schopoff S, Pasierbek P, Jantsch MF. RNA-regulated interaction of transportin-1 and exportin-5 with the double-stranded RNA-binding domain regulates nucleocytoplasmic shuttling of ADAR1. Mol Cell Biol. 2009 Mar;29(6):1487-97. doi: 10.1128/MCB.01519-08. Epub 2009 Jan, 5. PMID:19124606 doi:10.1128/MCB.01519-08
- ↑ Hsiao PW, Lin DL, Nakao R, Chang C. The linkage of Kennedy's neuron disease to ARA24, the first identified androgen receptor polyglutamine region-associated coactivator. J Biol Chem. 1999 Jul 16;274(29):20229-34. PMID:10400640
- ↑ Moroianu J, Blobel G, Radu A. Nuclear protein import: Ran-GTP dissociates the karyopherin alphabeta heterodimer by displacing alpha from an overlapping binding site on beta. Proc Natl Acad Sci U S A. 1996 Jul 9;93(14):7059-62. PMID:8692944
- ↑ Xia F, Canovas PM, Guadagno TM, Altieri DC. A survivin-ran complex regulates spindle formation in tumor cells. Mol Cell Biol. 2008 Sep;28(17):5299-311. Epub 2008 Jun 30. PMID:18591255 doi:10.1128/MCB.02039-07
- ↑ Sanz-Garcia M, Lopez-Sanchez I, Lazo PA. Proteomics identification of nuclear Ran GTPase as an inhibitor of human VRK1 and VRK2 (vaccinia-related kinase) activities. Mol Cell Proteomics. 2008 Nov;7(11):2199-214. doi: 10.1074/mcp.M700586-MCP200., Epub 2008 Jul 9. PMID:18617507 doi:10.1074/mcp.M700586-MCP200
- ↑ Hsiao PW, Lin DL, Nakao R, Chang C. The linkage of Kennedy's neuron disease to ARA24, the first identified androgen receptor polyglutamine region-associated coactivator. J Biol Chem. 1999 Jul 16;274(29):20229-34. PMID:10400640
- ↑ Moroianu J, Blobel G, Radu A. Nuclear protein import: Ran-GTP dissociates the karyopherin alphabeta heterodimer by displacing alpha from an overlapping binding site on beta. Proc Natl Acad Sci U S A. 1996 Jul 9;93(14):7059-62. PMID:8692944
- ↑ Xia F, Canovas PM, Guadagno TM, Altieri DC. A survivin-ran complex regulates spindle formation in tumor cells. Mol Cell Biol. 2008 Sep;28(17):5299-311. Epub 2008 Jun 30. PMID:18591255 doi:10.1128/MCB.02039-07
- ↑ Sanz-Garcia M, Lopez-Sanchez I, Lazo PA. Proteomics identification of nuclear Ran GTPase as an inhibitor of human VRK1 and VRK2 (vaccinia-related kinase) activities. Mol Cell Proteomics. 2008 Nov;7(11):2199-214. doi: 10.1074/mcp.M700586-MCP200., Epub 2008 Jul 9. PMID:18617507 doi:10.1074/mcp.M700586-MCP200
- ↑ Chook YM, Blobel G. Structure of the nuclear transport complex karyopherin-beta2-Ran x GppNHp. Nature. 1999 May 20;399(6733):230-7. PMID:10353245 doi:http://dx.doi.org/10.1038/20375
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