View source for 9tet


==Oligomerisation of type III CRISPR-associated Csx15 to regulate antiviral signalling==
<StructureSection load='9tet' size='340' side='right'caption='[[9tet]], [[Resolution|resolution]] 1.88&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9tet]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Pseudomonas_fluorescens Pseudomonas fluorescens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9TET OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9TET 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]] 1.88&#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=PO4:PHOSPHATE+ION'>PO4</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=9tet FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9tet OCA], [https://pdbe.org/9tet PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9tet RCSB], [https://www.ebi.ac.uk/pdbsum/9tet PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9tet ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
Prokaryotic type III CRISPR systems signal infection by generating cyclic oligoadenylate (cOA) second messengers, which activate defence proteins allosterically, providing immunity. cOA molecules are typically degraded by extrinsic, stand-alone ring nuclease (RN) enzymes with phosphodiesterase activity, or by the intrinsic RN activity of the effectors themselves. Viruses and plasmids also encode RNs, which can function as anti-CRISPRs (Acr). Eight different families of extrinsic RNs are currently known. Here, we report the structural and biochemical analysis of one of these families: Csx15. We show that Csx15 is a dimeric protein of the CARF (CRISPR associated Rossmann fold) superfamily with the ability to bind cyclic tetra-adenylate (cA4) molecules in a shared binding site formed by the head-to-tail stacking of dimers in a filament conformation. Some family members are non-enzymatic, relying on the sequestration (sponging) of cA4 to regulate the host immune response, while others act as canonical RNs, slowly degrading cA4.

The CRISPR ring nuclease Csx15 oligomerises on cyclic nucleotide binding to regulate antiviral defence.,White MF, McMahon SA, Chi H, Graham S Biochem J. 2026 Mar 30:BCJ20260019. doi: 10.1042/BCJ20260019. PMID:41911342<ref>PMID:41911342</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Pseudomonas fluorescens]]
[[Category: Chi H]]
[[Category: Graham S]]
[[Category: McMahon SA]]
[[Category: White MF]]