View source for 3luk


==Crystal structure of MID domain from hAGO2==
<StructureSection load='3luk' size='340' side='right' caption='[[3luk]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3luk]] is a 3 chain structure with sequence from [http://en.wikipedia.org/wiki/Human Human]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3LUK OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3LUK FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</scene></td></tr>
<tr id='NonStdRes'><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=MSE:SELENOMETHIONINE'>MSE</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[3luc|3luc]], [[3lud|3lud]], [[3lug|3lug]], [[3luh|3luh]], [[3luj|3luj]]</td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">EIF2C2, AGO2 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=9606 HUMAN])</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3luk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3luk OCA], [http://pdbe.org/3luk PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=3luk RCSB], [http://www.ebi.ac.uk/pdbsum/3luk PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=3luk ProSAT]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/AGO2_HUMAN AGO2_HUMAN]] Required for RNA-mediated gene silencing (RNAi) by the RNA-induced silencing complex (RISC). The 'minimal RISC' appears to include EIF2C2/AGO2 bound to a short guide RNA such as a microRNA (miRNA) or short interfering RNA (siRNA). These guide RNAs direct RISC to complementary mRNAs that are targets for RISC-mediated gene silencing. The precise mechanism of gene silencing depends on the degree of complementarity between the miRNA or siRNA and its target. Binding of RISC to a perfectly complementary mRNA generally results in silencing due to endonucleolytic cleavage of the mRNA specifically by EIF2C2/AGO2. Binding of RISC to a partially complementary mRNA results in silencing through inhibition of translation, and this is independent of endonuclease activity. May inhibit translation initiation by binding to the 7-methylguanosine cap, thereby preventing the recruitment of the translation initiation factor eIF4-E. May also inhibit translation initiation via interaction with EIF6, which itself binds to the 60S ribosomal subunit and prevents its association with the 40S ribosomal subunit. The inhibition of translational initiation leads to the accumulation of the affected mRNA in cytoplasmic processing bodies (P-bodies), where mRNA degradation may subsequently occur. In some cases RISC-mediated translational repression is also observed for miRNAs that perfectly match the 3' untranslated region (3'-UTR). Can also up-regulate the translation of specific mRNAs under certain growth conditions. Binds to the AU element of the 3'-UTR of the TNF (TNF-alpha) mRNA and up-regulates translation under conditions of serum starvation. Also required for transcriptional gene silencing (TGS), in which short RNAs known as antigene RNAs or agRNAs direct the transcriptional repression of complementary promoter regions.<ref>PMID:15105377</ref> <ref>PMID:15260970</ref> <ref>PMID:15337849</ref> <ref>PMID:15284456</ref> <ref>PMID:16271387</ref> <ref>PMID:16289642</ref> <ref>PMID:16142218</ref> <ref>PMID:16357216</ref> <ref>PMID:15800637</ref> <ref>PMID:16081698</ref> <ref>PMID:16936728</ref> <ref>PMID:16756390</ref> <ref>PMID:17382880</ref> <ref>PMID:17524464</ref> <ref>PMID:17932509</ref> <ref>PMID:17531811</ref> <ref>PMID:17507929</ref> <ref>PMID:18048652</ref> <ref>PMID:18771919</ref> <ref>PMID:18690212</ref> <ref>PMID:18178619</ref> <ref>PMID:19167051</ref>  
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/lu/3luk_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=3luk ConSurf].
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== Publication Abstract from PubMed ==
MicroRNAs (miRNAs) mediate post-transcriptional gene regulation through association with Argonaute proteins (AGOs). Crystal structures of archaeal and bacterial homologues of AGOs have shown that the MID (middle) domain mediates the interaction with the phosphorylated 5' end of the miRNA guide strand and this interaction is thought to be independent of the identity of the 5' nucleotide in these systems. However, analysis of the known sequences of eukaryotic miRNAs and co-immunoprecipitation experiments indicate that there is a clear bias for U or A at the 5' position. Here we report the crystal structure of a MID domain from a eukaryotic AGO protein, human AGO2. The structure, in complex with nucleoside monophosphates (AMP, CMP, GMP, and UMP) mimicking the 5' end of miRNAs, shows that there are specific contacts made between the base of UMP or AMP and a rigid loop in the MID domain. Notably, the structure of the loop discriminates against CMP and GMP and dissociation constants calculated from NMR titration experiments confirm these results, showing that AMP (0.26 mM) and UMP (0.12 mM) bind with up to 30-fold higher affinity than either CMP (3.6 mM) or GMP (3.3 mM). This study provides structural evidence for nucleotide-specific interactions in the MID domain of eukaryotic AGO proteins and explains the observed preference for U or A at the 5' end of miRNAs.

Structural basis for 5'-nucleotide base-specific recognition of guide RNA by human AGO2.,Frank F, Sonenberg N, Nagar B Nature. 2010 Jun 10;465(7299):818-22. Epub 2010 May 26. PMID:20505670<ref>PMID:20505670</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 3luk" style="background-color:#fffaf0;"></div>

==See Also==
*[[Argonaute|Argonaute]]
*[[Eukaryotic initiation factor|Eukaryotic initiation factor]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Human]]
[[Category: Frank, F]]
[[Category: Nagar, B]]
[[Category: Sonenberg, N]]
[[Category: Mid domain]]
[[Category: Ribonucleoprotein]]
[[Category: Rna binding protein]]
[[Category: Rna-binding]]
[[Category: Rna-mediated gene silencing]]
[[Category: Translation regulation]]