View source for 9lm3


==cryo-EM structure of retron Eco2==
<StructureSection load='9lm3' size='340' side='right'caption='[[9lm3]], [[Resolution|resolution]] 2.60&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9lm3]] is a 15 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9LM3 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9LM3 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]] 2.6&#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=9lm3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9lm3 OCA], [https://pdbe.org/9lm3 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9lm3 RCSB], [https://www.ebi.ac.uk/pdbsum/9lm3 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9lm3 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/RT67_ECOLX RT67_ECOLX] Reverse transcriptase (RT) component of antiviral defense system retron Ec67, minimally composed of a non-coding RNA (ncRNA) and this RT. Expression of these 2 elements confers protection against bacteriophage T5. At multiplicity of infection (MOI) of 0.02 cultures grow normally when infected with T5 without collapsing, at MOI 2 cultures enter growth stasis (PubMed:33157039). Responsible for synthesis of msDNA-Ec67 (a branched molecule with RNA linked by a 2',5'-phosphodiester bond to ssDNA). The retron transcript serves as primer (from a conserved internal G residue) and template for the reaction, and codes for the RT (PubMed:1378431, PubMed:1692831, PubMed:2466332). Can use other retrons as substrate (msDNA-Mx162 and msDNA-Ec86). Also able to synthesize DNA from a DNA template at least in vitro, although the enzyme is less active with a DNA template (PubMed:1692831).<ref>PMID:1378431</ref> <ref>PMID:1692831</ref> <ref>PMID:2466332</ref> <ref>PMID:33157039</ref> 
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== Publication Abstract from PubMed ==
In the evolutionary arms race between bacteria and viruses, retrons have emerged as distinctive antiphage defense systems. Here, we elucidate the structure and function of Retron-Eco2, which comprises a non-coding RNA (ncRNA) that encodes multicopy single-stranded DNA (msDNA, a DNAâRNA hybrid) and a fusion protein containing a reverse transcriptase (RT) domain and a topoisomerase-primase-like (Toprim) effector domain. The Eco2 msDNA and RT-Toprim fusion protein form a 1:1 stoichiometric nucleoprotein complex that further assembles into a trimer (msDNA:RT-Toprim ratio of 3:3) with a distinctive triangular configuration. The RNA portion of the msDNA in one protomer closely intertwines around the RT domain of an adjacent protomer, mediating the formation of this self-inhibitory assembly. Upon activation, the Toprim effector domain exhibits RNase activity, degrading RNA to arrest phage replication. We further reveal that phage mutants evading Eco2-mediated defense harbor mutations in the endonuclease IV-like protein DenB, underscoring DenB's critical role in triggering the activation of this system. Together, these findings provide key structural and functional insights into Retron-Eco2, laying the groundwork for harnessing its potential in biotechnology and synthetic biology applications.

Structural basis of the RNA-mediated Retron-Eco2 oligomerization.,Wang Y, Wang C, Yin Y, Cui Y, Dai Z, Liu C, Chen Y, Guan Z, Zou T Cell Discov. 2025 Sep 2;11(1):73. doi: 10.1038/s41421-025-00823-y. PMID:40897710<ref>PMID:40897710</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 9lm3" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Guan ZY]]
[[Category: Wang C]]
[[Category: Wang YJ]]
[[Category: Zou TT]]