The structure of ArdA

Experimental Data Snapshot

  • Resolution: 2.80 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 

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Extensive DNA Mimicry by the Arda Anti-Restriction Protein and its Role in the Spread of Antibiotic Resistance.

Mcmahon, S.A.Roberts, G.A.Johnson, K.A.Cooper, L.P.Liu, H.White, J.H.Carter, L.G.Sanghvi, B.Oke, M.Walkinshaw, M.D.Blakely, G.Naismith, J.H.Dryden, D.T.F.

(2009) Nucleic Acids Res 37: 4887

  • DOI: https://doi.org/10.1093/nar/gkp478
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The ardA gene, found in many prokaryotes including important pathogenic species, allows associated mobile genetic elements to evade the ubiquitous Type I DNA restriction systems and thereby assist the spread of resistance genes in bacterial populations. As such, ardA contributes to a major healthcare problem. We have solved the structure of the ArdA protein from the conjugative transposon Tn916 and find that it has a novel extremely elongated curved cylindrical structure with defined helical grooves. The high density of aspartate and glutamate residues on the surface follow a helical pattern and the whole protein mimics a 42-base pair stretch of B-form DNA making ArdA by far the largest DNA mimic known. Each monomer of this dimeric structure comprises three alpha-beta domains, each with a different fold. These domains have the same fold as previously determined proteins possessing entirely different functions. This DNA mimicry explains how ArdA can bind and inhibit the Type I restriction enzymes and we demonstrate that 6 different ardA from pathogenic bacteria can function in Escherichia coli hosting a range of different Type I restriction systems.

  • Organizational Affiliation

    Centre for Biomolecular Science, The University, St Andrews KY16 9ST, UK.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D
165Enterococcus faecalisMutation(s): 0 
Find proteins for Q47730 (Enterococcus faecalis)
Explore Q47730 
Go to UniProtKB:  Q47730
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ47730
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.80 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 63.81α = 90
b = 103.44β = 90
c = 172.98γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XDSdata scaling

Structure Validation

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Entry History 

Revision History  (Full details and data files)

  • Version 1.0: 2009-01-27
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 1.2: 2017-08-30
    Changes: Data collection
  • Version 1.3: 2024-05-08
    Changes: Data collection, Database references, Other, Refinement description