Structure of Acb2

Experimental Data Snapshot

  • Resolution: 2.69 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.249 
  • R-Value Observed: 0.250 

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Bacteriophages inhibit and evade cGAS-like immune function in bacteria.

Huiting, E.Cao, X.Ren, J.Athukoralage, J.S.Luo, Z.Silas, S.An, N.Carion, H.Zhou, Y.Fraser, J.S.Feng, Y.Bondy-Denomy, J.

(2023) Cell 186: 864

  • DOI: https://doi.org/10.1016/j.cell.2022.12.041
  • Primary Citation of Related Structures:  
    8H2J, 8H2X, 8H39

  • PubMed Abstract: 

    A fundamental strategy of eukaryotic antiviral immunity involves the cGAS enzyme, which synthesizes 2',3'-cGAMP and activates the effector STING. Diverse bacteria contain cGAS-like enzymes that produce cyclic oligonucleotides and induce anti-phage activity, known as CBASS. However, this activity has only been demonstrated through heterologous expression. Whether bacteria harboring CBASS antagonize and co-evolve with phages is unknown. Here, we identified an endogenous cGAS-like enzyme in Pseudomonas aeruginosa that generates 3',3'-cGAMP during phage infection, signals to a phospholipase effector, and limits phage replication. In response, phages express an anti-CBASS protein ("Acb2") that forms a hexamer with three 3',3'-cGAMP molecules and reduces phospholipase activity. Acb2 also binds to molecules produced by other bacterial cGAS-like enzymes (3',3'-cUU/UA/UG/AA) and mammalian cGAS (2',3'-cGAMP), suggesting broad inhibition of cGAS-based immunity. Upon Acb2 deletion, CBASS blocks lytic phage replication and lysogenic induction, but rare phages evade CBASS through major capsid gene mutations. Altogether, we demonstrate endogenous CBASS anti-phage function and strategies of CBASS inhibition and evasion.

  • Organizational Affiliation

    Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D, E
A, B, C, D, E, F
93Pseudomonas phage PaP2Mutation(s): 0 
Gene Names: orf26
Find proteins for A0A1C8HPQ3 (Pseudomonas phage PaMx33)
Explore A0A1C8HPQ3 
Go to UniProtKB:  A0A1C8HPQ3
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA0A1C8HPQ3
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
GOL (Subject of Investigation/LOI)
Query on GOL

Download Ideal Coordinates CCD File 
C3 H8 O3
EDO (Subject of Investigation/LOI)
Query on EDO

Download Ideal Coordinates CCD File 
G [auth A]
H [auth A]
J [auth B]
K [auth B]
L [auth C]
G [auth A],
H [auth A],
J [auth B],
K [auth B],
L [auth C],
M [auth C],
N [auth C],
O [auth D],
P [auth D],
Q [auth D],
R [auth E],
S [auth E],
T [auth F],
U [auth F]
C2 H6 O2
Experimental Data & Validation

Experimental Data

  • Resolution: 2.69 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.249 
  • R-Value Observed: 0.250 
  • Space Group: P 3 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 101.866α = 90
b = 101.866β = 90
c = 101.655γ = 120
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Natural Science Foundation of China (NSFC)China32171274

Revision History  (Full details and data files)

  • Version 1.0: 2023-02-22
    Type: Initial release
  • Version 1.1: 2023-03-08
    Changes: Database references