Structure of E. coli MS115-1 NucC, cAAA-bound form

Experimental Data Snapshot

  • Resolution: 1.67 Å
  • R-Value Free: 0.162 
  • R-Value Work: 0.142 
  • R-Value Observed: 0.143 

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This is version 1.4 of the entry. See complete history


Structure and Mechanism of a Cyclic Trinucleotide-Activated Bacterial Endonuclease Mediating Bacteriophage Immunity.

Lau, R.K.Ye, Q.Birkholz, E.A.Berg, K.R.Patel, L.Mathews, I.T.Watrous, J.D.Ego, K.Whiteley, A.T.Lowey, B.Mekalanos, J.J.Kranzusch, P.J.Jain, M.Pogliano, J.Corbett, K.D.

(2020) Mol Cell 77: 723

  • DOI: https://doi.org/10.1016/j.molcel.2019.12.010
  • Primary Citation of Related Structures:  
    6P7O, 6P7P, 6P7Q, 6Q1H, 6UXF, 6UXG

  • PubMed Abstract: 

    Bacteria possess an array of defenses against foreign invaders, including a broadly distributed bacteriophage defense system termed CBASS (cyclic oligonucleotide-based anti-phage signaling system). In CBASS systems, a cGAS/DncV-like nucleotidyltransferase synthesizes cyclic di- or tri-nucleotide second messengers in response to infection, and these molecules activate diverse effectors to mediate bacteriophage immunity via abortive infection. Here, we show that the CBASS effector NucC is related to restriction enzymes but uniquely assembles into a homotrimer. Binding of NucC trimers to a cyclic tri-adenylate second messenger promotes assembly of a NucC homohexamer competent for non-specific double-strand DNA cleavage. In infected cells, NucC activation leads to complete destruction of the bacterial chromosome, causing cell death prior to completion of phage replication. In addition to CBASS systems, we identify NucC homologs in over 30 type III CRISPR/Cas systems, where they likely function as accessory nucleases activated by cyclic oligoadenylate second messengers synthesized by these systems' effector complexes.

  • Organizational Affiliation

    Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA, USA.


Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
E. coli MS115-1 NucC 2-241
A, B, C
243Escherichia coli MS 115-1Mutation(s): 1 
Gene Names: HMPREF9540_01761
Find proteins for D7Y2H5 (Escherichia coli (strain MS 115-1))
Explore D7Y2H5 
Go to UniProtKB:  D7Y2H5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupD7Y2H5
Sequence Annotations
  • Reference Sequence

Find similar nucleic acids by:  Sequence   |   3D Structure  

Entity ID: 2
MoleculeChains LengthOrganismImage
Cyclic tri-AMP (5'-3' linked)
D, E, F
3Escherichia coli MS 115-1
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CL

Download Ideal Coordinates CCD File 
Experimental Data & Validation

Experimental Data

Unit Cell:
Length ( Å )Angle ( ˚ )
a = 131.592α = 90
b = 131.592β = 90
c = 252.109γ = 120
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: 2019-12-25
    Type: Initial release
  • Version 1.1: 2020-01-22
    Changes: Database references
  • Version 1.2: 2020-01-29
    Changes: Database references
  • Version 1.3: 2020-03-04
    Changes: Database references
  • Version 1.4: 2023-10-11
    Changes: Data collection, Database references, Refinement description