View source for 7d1a


==cryo-EM structure of a group II intron RNP complexed with its reverse transcriptase==
<StructureSection load='7d1a' size='340' side='right'caption='[[7d1a]], [[Resolution|resolution]] 3.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[7d1a]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Lactococcus_cremoris Lactococcus cremoris]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=7D1A OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=7D1A 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]] 3.8&#8491;</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=7d1a FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=7d1a OCA], [https://pdbe.org/7d1a PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=7d1a RCSB], [https://www.ebi.ac.uk/pdbsum/7d1a PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=7d1a ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/LTRA_LACLC LTRA_LACLC] Multifunctional protein that promotes group II intron splicing and mobility by acting both on RNA and DNA. It has three activities: reverse transcriptase (RT) for intron duplication, maturase to promote splicing, and DNA endonuclease for site-specific cleavage of recipient alleles. The intron-encoded protein promotes splicing by facilitating the formation of the catalytically active structure of the intron RNA. After splicing, the protein remains bound to the excised intron lariat RNA, forming ribonucleoprotein particles, and cleaving the antisense strand of the recipient DNA in the 3' exon. After DNA cleavage, retrohoming occurs by a target DNA-primed reverse transcription of the intron RNA that had reverse spliced into the sense strand of the recipient DNA. It also contributes to the recognition of the DNA target site and acts as a repressor of its own translation.
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== Publication Abstract from PubMed ==
Group II introns are the putative progenitors of nuclear spliceosomal introns and use the same two-step splicing pathway. In the cell, the intron RNA forms a ribonucleoprotein (RNP) complex with the intron-encoded protein (IEP), which is essential for splicing. Although structures of spliced group II intron RNAs and RNP complexes have been characterized, structural insights into the splicing process remain enigmatic due to lack of pre-catalytic structural models. Here, we report two cryo-EM structures of endogenously produced group II intron RNPs trapped in their pre-catalytic state. Comparison of the catalytically activated precursor RNP to its previously reported spliced counterpart allowed identification of key structural rearrangements accompanying splicing, including a remodeled active site and engagement of the exons. Importantly, altered RNA-protein interactions were observed upon splicing among the RNP complexes. Furthermore, analysis of the catalytically inert precursor RNP demonstrated the structural impact of the formation of the active site on RNP architecture. Taken together, our results not only fill a gap in understanding the structural basis of IEP-assisted group II intron splicing, but also provide parallels to evolutionarily related spliceosomal splicing.

Exon and protein positioning in a pre-catalytic group II intron RNP primed for splicing.,Liu N, Dong X, Hu C, Zeng J, Wang J, Wang J, Wang HW, Belfort M Nucleic Acids Res. 2020 Oct 6. pii: 5918319. doi: 10.1093/nar/gkaa773. PMID:33021674<ref>PMID:33021674</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 7d1a" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Lactococcus cremoris]]
[[Category: Large Structures]]
[[Category: Belfort M]]
[[Category: Dong XL]]
[[Category: Hu CX]]
[[Category: Liu N]]
[[Category: Wang HW]]
[[Category: Wang J]]
[[Category: Wang JW]]
[[Category: Zeng JW]]