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Crystal structure of human Karyopherin-beta2 bound to the PY-NLS of Saccharomyces cerevisiae NAB2
Structural highlights
FunctionTNPO1_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] Publication Abstract from PubMedImport-Karyopherin or Importin proteins bind nuclear localization signals (NLSs) to mediate the import of proteins into the cell nucleus. Karyopherin beta2 or Kapbeta2, also known as Transportin, is a member of this transporter family responsible for the import of numerous RNA binding proteins. Kapbeta2 recognizes a targeting signal termed the PY-NLS that lies within its cargos to target them through the nuclear pore complex. The recognition of PY-NLS by Kapbeta2 is conserved throughout eukaryotes. Kap104, the Kapbeta2 homolog in Saccharomyces cerevisiae, recognizes PY-NLSs in cargos Nab2, Hrp1, and Tfg2. We have determined the crystal structure of Kapbeta2 bound to the PY-NLS of the mRNA processing protein Nab2 at 3.05-A resolution. A seven-residue segment of the PY-NLS of Nab2 is observed to bind Kapbeta2 in an extended conformation and occupies the same PY-NLS binding site observed in other Kapbeta2.PY-NLS structures. Crystal structure of human Karyopherin beta2 bound to the PY-NLS of Saccharomyces cerevisiae Nab2.,Soniat M, Sampathkumar P, Collett G, Gizzi AS, Banu RN, Bhosle RC, Chamala S, Chowdhury S, Fiser A, Glenn AS, Hammonds J, Hillerich B, Khafizov K, Love JD, Matikainen B, Seidel RD, Toro R, Rajesh Kumar P, Bonanno JB, Chook YM, Almo SC J Struct Funct Genomics. 2013 Jun;14(2):31-5. doi: 10.1007/s10969-013-9150-1., Epub 2013 Mar 28. PMID:23535894[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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