Structure of VACV poxin 2'3' cGAMP-specific nuclease

Experimental Data Snapshot

  • Resolution: 1.70 Å
  • R-Value Free: 0.182 
  • R-Value Work: 0.160 
  • R-Value Observed: 0.160 

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Viral and metazoan poxins are cGAMP-specific nucleases that restrict cGAS-STING signalling.

Eaglesham, J.B.Pan, Y.Kupper, T.S.Kranzusch, P.J.

(2019) Nature 566: 259-263

  • DOI: https://doi.org/10.1038/s41586-019-0928-6
  • Primary Citation of Related Structures:  
    6EA6, 6EA8, 6EA9

  • PubMed Abstract: 

    Cytosolic DNA triggers innate immune responses through the activation of cyclic GMP-AMP synthase (cGAS) and production of the cyclic dinucleotide second messenger 2',3'-cyclic GMP-AMP (cGAMP) 1-4 . 2',3'-cGAMP is a potent inducer of immune signalling; however, no intracellular nucleases are known to cleave 2',3'-cGAMP and prevent the activation of the receptor stimulator of interferon genes (STING) 5-7 . Here we develop a biochemical screen to analyse 24 mammalian viruses, and identify poxvirus immune nucleases (poxins) as a family of 2',3'-cGAMP-degrading enzymes. Poxins cleave 2',3'-cGAMP to restrict STING-dependent signalling and deletion of the poxin gene (B2R) attenuates vaccinia virus replication in vivo. Crystal structures of vaccinia virus poxin in pre- and post-reactive states define the mechanism of selective 2',3'-cGAMP degradation through metal-independent cleavage of the 3'-5' bond, converting 2',3'-cGAMP into linear Gp[2'-5']Ap[3']. Poxins are conserved in mammalian poxviruses. In addition, we identify functional poxin homologues in the genomes of moths and butterflies and the baculoviruses that infect these insects. Baculovirus and insect host poxin homologues retain selective 2',3'-cGAMP degradation activity, suggesting an ancient role for poxins in cGAS-STING regulation. Our results define poxins as a family of 2',3'-cGAMP-specific nucleases and demonstrate a mechanism for how viruses evade innate immunity.

  • Organizational Affiliation

    Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein B2A,
B [auth C],
C [auth B],
220Vaccinia virus WRMutation(s): 0 
Gene Names: VACWR184B2R
Find proteins for Q01225 (Vaccinia virus (strain Western Reserve))
Explore Q01225 
Go to UniProtKB:  Q01225
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ01225
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
B [auth C],
C [auth B],
Experimental Data & Validation

Experimental Data

  • Resolution: 1.70 Å
  • R-Value Free: 0.182 
  • R-Value Work: 0.160 
  • R-Value Observed: 0.160 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 55.026α = 90
b = 93.194β = 105.63
c = 94.133γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2019-02-06
    Type: Initial release
  • Version 1.1: 2019-02-20
    Changes: Data collection, Database references
  • Version 1.2: 2019-02-27
    Changes: Data collection, Database references
  • Version 1.3: 2019-12-11
    Changes: Derived calculations