9tet

Oligomerisation of type III CRISPR-associated Csx15 to regulate antiviral signalling

spinqualitylabelsall models 9tet, resolution 1.88Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9tet is a 1 chain structure with sequence from Pseudomonas fluorescens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.88Å Ligands: GOL, PO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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