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==Inhibition by ATP regulates the activity of a CBASS antiphage nucleotide cyclase==
<StructureSection load='9sa4' size='340' side='right'caption='[[9sa4]], [[Resolution|resolution]] 2.23&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9sa4]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Bacillus_cereus Bacillus cereus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9SA4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9SA4 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]] 2.23&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ATP:ADENOSINE-5-TRIPHOSPHATE'>ATP</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=9sa4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9sa4 OCA], [https://pdbe.org/9sa4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9sa4 RCSB], [https://www.ebi.ac.uk/pdbsum/9sa4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9sa4 ProSAT]</span></td></tr>
</table>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The bacterial anti-phage immune system is complex, diverse, and in several important cases ancestral to that found in eukaryotes, including humans. One example is CBASS (cyclic oligonucleotide based anti-phage signalling system), a widespread bacterial defence that signals phage presence in the cell via cyclic nucleotide second messengers, activating ancillary effectors to combat infection. CBASS is homologous and ancestral to the eukaryotic cGAS/STING pathway for antiviral defence. The heart of the system is a nucleotide cyclase known as a cGAS/DncV-like nucleotidyltransferase, which is activated by phage infection. The mechanisms of activation of CBASS cyclases are diverse and in most cases not fully understood at a molecular level. Moreover, it is vital to keep these signal-generating enzymes fully inactive in the absence of phage infection to avoid auto-toxicity. Here, we report a structural and mechanistic study of a CBASS cyclase from Bacillus cereus. Using crystal structures of key reaction intermediates, coupled with kinetic analyses, we show that the substrate, ATP, plays a fundamental role in the inhibition of the non-activated form of the enzyme in vitro. We provide a molecular explanation for this regulation and explore the implications for the regulation of these important defence systems in bacterial immunity.

Inhibition by ATP regulates the activity of a CBASS anti-phage nucleotide cyclase.,Gaskell-Mew L, McQuarrie S, McMahon SA, Wotherspoon P, Graham S, Gloster TM, White MF Biochem J. 2026 Aug 5;483(8):1617-1630. doi: 10.1042/BCJ20260457. PMID:42496152<ref>PMID:42496152</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9sa4" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Bacillus cereus]]
[[Category: Large Structures]]
[[Category: Gaskell-Mew L]]
[[Category: Gloster TM]]
[[Category: Graham S]]
[[Category: McMahon SA]]
[[Category: McQuarrie S]]
[[Category: White MF]]
[[Category: Wotherspoon P]]