1Y7Y

High-resolution crystal structure of the restriction-modification controller protein C.AhdI from Aeromonas hydrophila


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.69 Å
  • R-Value Free: 0.223 
  • R-Value Work: 0.169 

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This is version 1.3 of the entry. See complete history


Literature

High-resolution crystal structure of the restriction-modification controller protein C.AhdI from Aeromonas hydrophila.

McGeehan, J.E.Streeter, S.D.Papapanagiotou, I.Fox, G.C.Kneale, G.G.

(2005) J Mol Biol 346: 689-701

  • DOI: https://doi.org/10.1016/j.jmb.2004.12.025
  • Primary Citation of Related Structures:  
    1Y7Y

  • PubMed Abstract: 

    Restriction-modification (R-M) systems serve to protect the host bacterium from invading bacteriophage. The multi-component system includes a methyltransferase, which recognizes and methylates a specific DNA sequence, and an endonuclease which recognises the same sequence and cleaves within or close to this site. The endonuclease will only cleave DNA that is unmethylated at the specific site, thus host DNA is protected while non-host DNA is cleaved. However, following DNA replication, expression of the endonuclease must be delayed until the host DNA is appropriately methylated. In many R-M systems, this regulation is achieved at the transcriptional level via the controller protein, or C-protein. We have solved the first X-ray structure of an R-M controller protein, C.AhdI, to 1.69 A resolution using selenomethionine MAD. C.AhdI is part of a Type IIH R-M system from the pathogen Aeromonas hydrophila. The structure reveals an all-alpha protein that contains a classical helix-turn-helix (HTH) domain and can be assigned to the Xre family of transcriptional regulators. Unlike its monomeric structural homologues, an extended helix generates an interface that results in dimerisation of the free protein. The dimer is electrostatically polarised and a positively charged surface corresponds to the position of the DNA recognition helices of the HTH domain. Comparison with the structure of the lambda cI ternary complex suggests that C.AhdI activates transcription through direct contact with the sigma70 subunit of RNA polymerase.


  • Organizational Affiliation

    Biophysics Laboratories, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, PO1 2DT, UK.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
C.AhdI
A, B
74Aeromonas hydrophilaMutation(s): 0 
UniProt
Find proteins for Q7X0F0 (Aeromonas hydrophila)
Explore Q7X0F0 
Go to UniProtKB:  Q7X0F0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ7X0F0
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.69 Å
  • R-Value Free: 0.223 
  • R-Value Work: 0.169 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 24.403α = 90
b = 57.246β = 98.89
c = 46.125γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
MOLREPphasing
REFMACrefinement
CCP4data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2005-02-22
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2024-02-14
    Changes: Data collection, Database references