View source for 6gb2


==Unique features of mammalian mitochondrial translation initiation revealed by cryo-EM. This file contains the 39S ribosomal subunit.==
<SX load='6gb2' size='340' side='right' viewer='molstar' caption='[[6gb2]], [[Resolution|resolution]] 3.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6gb2]] is a 16 chain structure with sequence from [https://en.wikipedia.org/wiki/Sus_scrofa Sus scrofa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6GB2 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6GB2 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 3.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=5GP:GUANOSINE-5-MONOPHOSPHATE'>5GP</scene>, <scene name='pdbligand=FME:N-FORMYLMETHIONINE'>FME</scene>, <scene name='pdbligand=GSP:5-GUANOSINE-DIPHOSPHATE-MONOTHIOPHOSPHATE'>GSP</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</scene>, <scene name='pdbligand=SPM:SPERMINE'>SPM</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</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=6gb2 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6gb2 OCA], [https://pdbe.org/6gb2 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6gb2 RCSB], [https://www.ebi.ac.uk/pdbsum/6gb2 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6gb2 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A0A4X1U6S6_PIG A0A4X1U6S6_PIG] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Mitochondria maintain their own specialized protein synthesis machinery, which in mammals is used exclusively for the synthesis of the membrane proteins responsible for oxidative phosphorylation(1,2). The initiation of protein synthesis in mitochondria differs substantially from bacterial or cytosolic translation systems. Mitochondrial translation initiation lacks initiation factor 1, which is essential in all other translation systems from bacteria to mammals(3,4). Furthermore, only one type of methionyl transfer RNA (tRNA(Met)) is used for both initiation and elongation(4,5), necessitating that the initiation factor specifically recognizes the formylated version of tRNA(Met) (fMet-tRNA(Met)). Lastly, most mitochondrial mRNAs do not possess 5' leader sequences to promote mRNA binding to the ribosome(2). There is currently little mechanistic insight into mammalian mitochondrial translation initiation, and it is not clear how mRNA engagement, initiator-tRNA recruitment and start-codon selection occur. Here we determine the cryo-EM structure of the complete translation initiation complex from mammalian mitochondria at 3.2 A. We describe the function of an additional domain insertion that is present in the mammalian mitochondrial initiation factor 2 (mtIF2). By closing the decoding centre, this insertion stabilizes the binding of leaderless mRNAs and induces conformational changes in the rRNA nucleotides involved in decoding. We identify unique features of mtIF2 that are required for specific recognition of fMet-tRNA(Met) and regulation of its GTPase activity. Finally, we observe that the ribosomal tunnel in the initiating ribosome is blocked by insertion of the N-terminal portion of mitochondrial protein mL45, which becomes exposed as the ribosome switches to elongation mode and may have an additional role in targeting of mitochondrial ribosomes to the protein-conducting pore in the inner mitochondrial membrane.

Unique features of mammalian mitochondrial translation initiation revealed by cryo-EM.,Kummer E, Leibundgut M, Rackham O, Lee RG, Boehringer D, Filipovska A, Ban N Nature. 2018 Aug;560(7717):263-267. doi: 10.1038/s41586-018-0373-y. Epub 2018 Aug, 8. PMID:30089917<ref>PMID:30089917</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6gb2" style="background-color:#fffaf0;"></div>

==See Also==
*[[Ribosome 3D structures|Ribosome 3D structures]]
== References ==
<references/>
__TOC__
</SX>
[[Category: Large Structures]]
[[Category: Sus scrofa]]
[[Category: Ban N]]
[[Category: Boehringer D]]
[[Category: Kummer E]]
[[Category: Leibundgut M]]