View source for 7z56


==Crystal Structure of the Ring Nuclease 0455 from Sulfolobus islandicus (Sis0455) in its apo form==
<StructureSection load='7z56' size='340' side='right'caption='[[7z56]], [[Resolution|resolution]] 2.27&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[7z56]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Sulfolobus_islandicus_REY15A Sulfolobus islandicus REY15A]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=7Z56 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=7Z56 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]] 2.27&#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=7z56 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=7z56 OCA], [https://pdbe.org/7z56 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=7z56 RCSB], [https://www.ebi.ac.uk/pdbsum/7z56 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=7z56 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/F0NGX6_SULIR F0NGX6_SULIR] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Standalone ring nucleases are CRISPR ancillary proteins, which downregulate the immune response of Type III CRISPR-Cas systems by cleaving cyclic oligoadenylates (cA) second messengers. Two genes with this function have been found within the Sulfolobus islandicus (Sis) genome. They code for a long polypeptide composed by a CARF domain fused to an HTH domain and a short polypeptide constituted by a CARF domain with a 40 residue C-terminal insertion. Here, we determine the structure of the apo and substrate bound states of the Sis0455 enzyme, revealing an insertion at the C-terminal region of the CARF domain, which plays a key role closing the catalytic site upon substrate binding. Our analysis reveals the key residues of Sis0455 during cleavage and the coupling of the active site closing with their positioning to proceed with cA4 phosphodiester hydrolysis. A time course comparison of cA4 cleavage between the short, Sis0455, and long ring nucleases, Sis0811, shows the slower cleavage kinetics of the former, suggesting that the combination of these two types of enzymes with the same function in a genome could be an evolutionary strategy to regulate the levels of the second messenger in different infection scenarios.

Molecular basis of cyclic tetra-oligoadenylate processing by small standalone CRISPR-Cas ring nucleases.,Molina R, Garcia-Martin R, Lopez-Mendez B, Jensen ALG, Ciges-Tomas JR, Marchena-Hurtado J, Stella S, Montoya G Nucleic Acids Res. 2022 Oct 28;50(19):11199-11213. doi: 10.1093/nar/gkac923. PMID:36271789<ref>PMID:36271789</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 7z56" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Sulfolobus islandicus REY15A]]
[[Category: Jensen ALG]]
[[Category: Lopez-Mendez B]]
[[Category: Marchena-Hurtado J]]
[[Category: Martin-Garcia R]]
[[Category: Molina R]]
[[Category: Montoya G]]
[[Category: Stella S]]