A viral anti-CRISPR subverts type III CRISPR immunity by rapid degradation of cyclic oligoadenylate

Experimental Data Snapshot

  • Resolution: 1.55 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.204 

wwPDB Validation   3D Report Full Report

This is version 1.4 of the entry. See complete history


An anti-CRISPR viral ring nuclease subverts type III CRISPR immunity.

Athukoralage, J.S.McMahon, S.A.Zhang, C.Gruschow, S.Graham, S.Krupovic, M.Whitaker, R.J.Gloster, T.M.White, M.F.

(2020) Nature 577: 572-575

  • DOI: https://doi.org/10.1038/s41586-019-1909-5
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The CRISPR system in bacteria and archaea provides adaptive immunity against mobile genetic elements. Type III CRISPR systems detect viral RNA, resulting in the activation of two regions of the Cas10 protein: an HD nuclease domain (which degrades viral DNA) 1,2 and a cyclase domain (which synthesizes cyclic oligoadenylates from ATP) 3-5 . Cyclic oligoadenylates in turn activate defence enzymes with a CRISPR-associated Rossmann fold domain 6 , sculpting a powerful antiviral response 7-10 that can drive viruses to extinction 7,8 . Cyclic nucleotides are increasingly implicated in host-pathogen interactions 11-13 . Here we identify a new family of viral anti-CRISPR (Acr) enzymes that rapidly degrade cyclic tetra-adenylate (cA 4 ). The viral ring nuclease AcrIII-1 is widely distributed in archaeal and bacterial viruses and in proviruses. The enzyme uses a previously unknown fold to bind cA 4 specifically, and a conserved active site to rapidly cleave this signalling molecule, allowing viruses to neutralize the type III CRISPR defence system. The AcrIII-1 family has a broad host range, as it targets cA 4 signalling molecules rather than specific CRISPR effector proteins. Our findings highlight the crucial role of cyclic nucleotide signalling in the conflict between viruses and their hosts.

  • Organizational Affiliation

    Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, Fife, UK.


Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Uncharacterized protein
A, B, C, D, E
A, B, C, D, E, F, G, H
138Sulfolobus islandicus rod-shaped virus 1Mutation(s): 0 
Gene Names: 114
Find proteins for Q8QL27 (Sulfolobus islandicus rod-shaped virus 1)
Explore Q8QL27 
Go to UniProtKB:  Q8QL27
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8QL27
Sequence Annotations
  • Reference Sequence

Find similar nucleic acids by:  Sequence   |   3D Structure  

Entity ID: 2
MoleculeChains LengthOrganismImage
cyclic oligoadenylateI [auth K],
J [auth I],
K [auth L],
L [auth M]
4synthetic construct
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.55 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.204 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 49.829α = 80.22
b = 51.727β = 89.68
c = 85.611γ = 83.38
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
xia2data reduction
xia2data scaling

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Biotechnology and Biological Sciences Research CouncilUnited KingdomBB/R008035/1
Biotechnology and Biological Sciences Research CouncilUnited KingdomBB/S000313/1

Revision History  (Full details and data files)

  • Version 1.0: 2019-10-30
    Type: Initial release
  • Version 1.1: 2020-01-15
    Changes: Database references
  • Version 1.2: 2020-01-29
    Changes: Database references
  • Version 1.3: 2020-02-05
    Changes: Database references
  • Version 1.4: 2024-01-24
    Changes: Data collection, Database references, Refinement description