View source for 9asi


==Cryo-EM structure of the active Lactococcus lactis Csm bound to target in pre-cleavage stage==
<StructureSection load='9asi' size='340' side='right'caption='[[9asi]], [[Resolution|resolution]] 2.79&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9asi]] is a 12 chain structure with sequence from [https://en.wikipedia.org/wiki/Lactococcus_lactis_subsp._lactis Lactococcus lactis subsp. lactis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9ASI OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9ASI 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]] 2.79&#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=9asi FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9asi OCA], [https://pdbe.org/9asi PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9asi RCSB], [https://www.ebi.ac.uk/pdbsum/9asi PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9asi ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/L0CFH1_LACLL L0CFH1_LACLL] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The type III-A (Csm) CRISPR-Cas systems are multi-subunit and multipronged prokaryotic enzymes in guarding the hosts against viral invaders. Beyond cleaving activator RNA transcripts, Csm confers two additional activities: shredding single-stranded DNA and synthesizing cyclic oligoadenylates (cOAs) by the Cas10 subunit. Known Cas10 enzymes exhibit a fascinating diversity in cOA production. Three major forms-cA3, cA4 and cA6have been identified, each with the potential to trigger unique downstream effects. Whereas the mechanism for cOA-dependent activation is well characterized, the molecular basis for synthesizing different cOA isoforms remains unclear. Here, we present structural characterization of a cA6-producing Csm complex during its activation by an activator RNA. Analysis of the captured intermediates of cA6 synthesis suggests a 3'-to-5' nucleotidyl transferring process. Three primary adenine binding sites can be identified along the chain elongation path, including a unique tyrosine-threonine dyad found only in the cA6-producing Cas10. Consistently, disrupting the tyrosine-threonine dyad specifically impaired cA6 production while promoting cA4 production. These findings suggest that Cas10 utilizes a unique enzymatic mechanism for forming the phosphodiester bond and has evolved distinct strategies to regulate the cOA chain length.

Molecular basis for cA6 synthesis by a type III-A CRISPR-Cas enzyme and its conversion to cA4 production.,Goswami HN, Ahmadizadeh F, Wang B, Addo-Yobo D, Zhao Y, Whittington AC, He H, Terns MP, Li H Nucleic Acids Res. 2024 Jul 11:gkae603. doi: 10.1093/nar/gkae603. PMID:38989619<ref>PMID:38989619</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9asi" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Lactococcus lactis subsp. lactis]]
[[Category: Large Structures]]
[[Category: Goswami HN]]
[[Category: Li H]]
[[Category: Wang B]]