1xk5

<table><tr><td colspan='2'>[[1xk5]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Human Human]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XK5 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1XK5 FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=TPG:2,2,7-TRIMETHYL-GUANOSINE-5-TRIPHOSPHATE-5-GUANOSINE'>TPG</scene></td></tr>

[[https://www.uniprot.org/uniprot/SPN1_HUMAN SPN1_HUMAN]] Functions as an U snRNP-specific nuclear import adapter. Involved in the trimethylguanosine (m3G)-cap-dependent nuclear import of U snRNPs. Binds specifically to the terminal m3G-cap U snRNAs.<ref>PMID:9670026</ref>

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== Publication Abstract from PubMed ==

In higher eukaryotes the biogenesis of spliceosomal UsnRNPs involves a nucleocytoplasmic shuttling cycle. After the m7G-cap-dependent export of the snRNAs U1, U2, U4 and U5 to the cytoplasm, each of these snRNAs associates with seven Sm proteins. Subsequently, the m7G-cap is hypermethylated to the 2,2,7-trimethylguanosine (m3G)-cap. The import adaptor snurportin1 recognises the m3G-cap and facilitates the nuclear import of the UsnRNPs by binding to importin-beta. Here we report the crystal structure of the m3G-cap-binding domain of snurportin1 with bound m3GpppG at 2.4 A resolution, revealing a structural similarity to the mRNA-guanyly-transferase. Snurportin1 binds both the hypermethylated cap and the first nucleotide of the RNA in a stacked conformation. This binding mode differs significantly from that of the m7G-cap-binding proteins Cap-binding protein 20 (CBP20), eukaryotic initiation factor 4E (eIF4E) and viral protein 39 (VP39). The specificity of the m3G-cap recognition by snurportin1 was evaluated by fluorescence spectroscopy, demonstrating the importance of a highly solvent exposed tryptophan for the discrimination of m7G-capped RNAs. The critical role of this tryptophan and as well of a tryptophan continuing the RNA base stack was confirmed by nuclear import assays and cap-binding activity tests using several snurportin1 mutants.

Structural basis for m3G-cap-mediated nuclear import of spliceosomal UsnRNPs by snurportin1.,Strasser A, Dickmanns A, Luhrmann R, Ficner R EMBO J. 2005 Jul 6;24(13):2235-43. Epub 2005 May 26. PMID:15920472<ref>PMID:15920472</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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<div class="pdbe-citations 1xk5" style="background-color:#fffaf0;"></div>

[[Category: Human]]

[[Category: Dickmanns, A]]

[[Category: Ficner, R]]

[[Category: Luehrmann, R]]

[[Category: Strasser, A]]

[[Category: Transport protein]]