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8fm1

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Structure of CBASS Cap5 from Pseudomonas syringae in the absence of a ligand (apo form dimer)

Structural highlights

8fm1 is a 12 chain structure with sequence from Pseudomonas syringae. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 3.16Å
Ligands:
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

A0A2P0QGK5_PSESF

Publication Abstract from PubMed

The bacterial cyclic oligonucleotide-based antiphage signaling system (CBASS) is similar to the cGAS-STING system in humans, containing an enzyme that synthesizes a cyclic nucleotide on viral infection and an effector that senses the second messenger for the antiviral response. Cap5, containing a SAVED domain coupled to an HNH DNA endonuclease domain, is the most abundant CBASS effector, yet the mechanism by which it becomes activated for cell killing remains unknown. We present here high-resolution structures of full-length Cap5 from Pseudomonas syringae (Ps) with second messengers. The key to PsCap5 activation is a dimer-to-tetramer transition, whereby the binding of second messenger to dimer triggers an open-to-closed transformation of the SAVED domains, furnishing a surface for assembly of the tetramer. This movement propagates to the HNH domains, juxtaposing and converting two HNH domains into states for DNA destruction. These results show how Cap5 effects bacterial cell suicide and we provide proof-in-principle data that the CBASS can be extrinsically activated to limit bacterial infections.

Activation of CBASS Cap5 endonuclease immune effector by cyclic nucleotides.,Rechkoblit O, Sciaky D, Kreitler DF, Buku A, Kottur J, Aggarwal AK Nat Struct Mol Biol. 2024 May;31(5):767-776. doi: 10.1038/s41594-024-01220-x. , Epub 2024 Feb 6. PMID:38321146^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Rechkoblit O, Sciaky D, Kreitler DF, Buku A, Kottur J, Aggarwal AK. Activation of CBASS Cap5 endonuclease immune effector by cyclic nucleotides. Nat Struct Mol Biol. 2024 May;31(5):767-776. PMID:38321146 doi:10.1038/s41594-024-01220-x