Crystal structure of the GT domain of Clostridium difficile Toxin A

Experimental Data Snapshot

  • Resolution: 1.50 Å
  • R-Value Free: 0.214 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.191 

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The structure of Clostridium difficile toxin A glucosyltransferase domain bound to Mn2+ and UDP provides insights into glucosyltransferase activity and product release.

D'Urzo, N.Malito, E.Biancucci, M.Bottomley, M.J.Maione, D.Scarselli, M.Martinelli, M.

(2012) FEBS J 279: 3085-3097

  • DOI: https://doi.org/10.1111/j.1742-4658.2012.08688.x
  • Primary Citation of Related Structures:  
    4DMV, 4DMW

  • PubMed Abstract: 

    Clostridiumdifficile toxin A (TcdA) is a member of the large clostridial toxin family, and is responsible, together with C. difficile toxin B (TcdB), for many clinical symptoms d ring human infections. Like other large clostridial toxins, TcdA catalyzes the glucosylation of GTPases, and is able to inactivate small GTPases within the host cell. Here, we report the crystal structures of the TcdA glucosyltransferase domain (TcdA-GT) in the apo form and in the presence of Mn(2+) and hydrolyzed UDP-glucose. These structures, together with the recently reported crystal structure of TcdA-GT bound to UDP-glucose, provide a detailed understanding of the conformational changes of TcdA that occur during the catalytic cycle. Indeed, we present a new intermediate conformation of a so-called 'lid' loop (residues 510-522 in TcdA), concomitant with the absence of glucose in the catalytic domain. The recombinant TcdA was expressed in Brevibacillus in the inactive apo form. High thermal stability of wild-type TcdA was observed only after the addition of both Mn(2+) and UDP-glucose. The glucosylhydrolase activity, which is readily restored after reconstitution with both these cofactors, was similar to that reported for TcdB. Interestingly, we found that ammonium, like K(+) , is able to activate the UDP-glucose hydrolase activities of TcdA. Consequently, the presence of ammonium in the crystallization buffer enabled us to obtain the first crystal structure of TcdA-GT bound to the hydrolysis product UDP.

  • Organizational Affiliation

    Novartis Vaccines and Diagnostics, Siena, Italy.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Toxin A556Clostridioides difficileMutation(s): 0 
Gene Names: toxAtcdA
EC: 2.4.1
Find proteins for P16154 (Clostridioides difficile)
Explore P16154 
Go to UniProtKB:  P16154
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP16154
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.50 Å
  • R-Value Free: 0.214 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.191 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 66.08α = 90
b = 153.03β = 90
c = 66.26γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
PDB_EXTRACTdata extraction
MxCuBEdata collection

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-07-18
    Type: Initial release
  • Version 1.1: 2012-10-31
    Changes: Database references
  • Version 1.2: 2023-09-13
    Changes: Data collection, Database references, Refinement description