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==Complex of C. elegans eIF4E-3 with the 4E-binding protein Mextli==
<StructureSection load='5aby' size='340' side='right'caption='[[5aby]], [[Resolution|resolution]] 1.95&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5aby]] is a 6 chain structure with sequence from [https://en.wikipedia.org/wiki/Caenorhabditis_elegans Caenorhabditis elegans]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5ABY OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5ABY FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.95&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5aby FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5aby OCA], [https://pdbe.org/5aby PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5aby RCSB], [https://www.ebi.ac.uk/pdbsum/5aby PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5aby ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/IF4E3_CAEEL IF4E3_CAEEL] Recognizes and binds the 7-methylguanosine-containing mRNA cap during an early step in the initiation of protein synthesis and facilitates ribosome binding by inducing the unwinding of the mRNAs secondary structures. All 5 eIF4E proteins bind monomethyl cap structures. Only ife-1, ife-2 and ife-5 bind trimethyl cap structures which result from trans-splicing. Translation of trimethyl cap structure mRNAs may be regulated by intracellular redox state; disulfide bonds change the width and depth of the cap-binding cavity determining selectivity to mRNA caps. Ife-3 is essential for viability.<ref>PMID:10744754</ref> <ref>PMID:12422237</ref> <ref>PMID:9553113</ref> 
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== Publication Abstract from PubMed ==
The eIF4E-binding proteins (4E-BPs) are a diverse class of translation regulators that share a canonical eIF4E-binding motif (4E-BM) with eIF4G. Consequently, they compete with eIF4G for binding to eIF4E, thereby inhibiting translation initiation. Mextli (Mxt) is an unusual 4E-BP that promotes translation by also interacting with eIF3. Here we present the crystal structures of the eIF4E-binding regions of the Drosophila melanogaster (Dm) and Caenorhabditis elegans (Ce) Mxt proteins in complex with eIF4E in the cap-bound and cap-free states. The structures reveal unexpected evolutionary plasticity in the eIF4E-binding mode, with a classical bipartite interface for Ce Mxt and a novel tripartite interface for Dm Mxt. Both interfaces comprise a canonical helix and a noncanonical helix that engage the dorsal and lateral surfaces of eIF4E, respectively. Remarkably, Dm Mxt contains a C-terminal auxiliary helix that lies anti-parallel to the canonical helix on the eIF4E dorsal surface. In contrast to the eIF4G and Ce Mxt complexes, the Dm eIF4E-Mxt complexes are resistant to competition by bipartite 4E-BPs, suggesting that Dm Mxt can bind eIF4E when eIF4G binding is inhibited. Our results uncovered unexpected diversity in the binding modes of 4E-BPs, resulting in eIF4E complexes that display differential sensitivity to 4E-BP regulation.

Mextli proteins use both canonical bipartite and novel tripartite binding modes to form eIF4E complexes that display differential sensitivity to 4E-BP regulation.,Peter D, Weber R, Kone C, Chung MY, Ebertsch L, Truffault V, Weichenrieder O, Igreja C, Izaurralde E Genes Dev. 2015 Aug 20. PMID:26294658<ref>PMID:26294658</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 5aby" style="background-color:#fffaf0;"></div>

==See Also==
*[[Eukaryotic initiation factor 3D structures|Eukaryotic initiation factor 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Caenorhabditis elegans]]
[[Category: Large Structures]]
[[Category: Peter D]]
[[Category: Weichenrieder O]]