1YNT

Structure of the monomeric form of T. gondii SAG1 surface antigen bound to a human Fab


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.10 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.241 

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This is version 1.6 of the entry. See complete history


Literature

Crystal structure of the complex between the monomeric form of Toxoplasma gondii surface antigen 1 (SAG1) and a monoclonal antibody that mimics the human immune response

Graille, M.Stura, E.A.Bossus, M.Muller, B.H.Letourneur, O.Battail-Poirot, N.Sibai, G.Gauthier, M.Rolland, D.Le Du, M.H.Ducancel, F.

(2005) J Mol Biol 354: 447-458

  • DOI: https://doi.org/10.1016/j.jmb.2005.09.028
  • Primary Citation of Related Structures:  
    1YNT

  • PubMed Abstract: 

    Toxoplasma gondii, the intracellular parasite responsible for toxoplasmosis infects more than one-third of the world population and can be life-threatening for fetuses and immunocompromised patients. The surface protein SAG1 is an important immune target, which provides a strong immune response against the invasive tachyzoite while the other forms of the parasite, devoid of SAG1 at their surface, are multiplying. In addition to this role as a "hot spot" decoy, SAG1 is predicted to act as an adhesin during host-cell attachment through its binding to proteoglycans. To begin to understand the relationships between SAG1 epitopes and the ligand-binding site, we have solved the crystal structure of the monomeric form of T.gondii SAG1 complexed to a Fab derived from a monoclonal antibody raised against tachyzoite particles. This antibody competes strongly with human Toxoplasma-specific sera, suggesting that its epitope is part of an immunodominant region present on the surface of SAG1. The structure reveals that this conformational epitope, located within the SAG1 N-terminal domain, does not overlap with the proposed ligand-binding pocket. This study provides the first structural description of the monomeric form of SAG1, and significant insights into its dual role of adhesin and immune target during parasite infection.


  • Organizational Affiliation

    Département d'Ingénierie et d'Etudes des Protéines, Centre d'Etudes de Saclay, 91191 Gif-sur-Yvette, France.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
4F11E12 Fab variable light chain region
A, C
213Mus musculusMutation(s): 0 
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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
4F11E12 Fab variable heavy chain region
B, D
218Mus musculusMutation(s): 0 
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Entity ID: 3
MoleculeChains Sequence LengthOrganismDetailsImage
protein L61Finegoldia magna ATCC 29328Mutation(s): 0 
UniProt
Find proteins for Q51918 (Finegoldia magna)
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UniProt GroupQ51918
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Entity ID: 4
MoleculeChains Sequence LengthOrganismDetailsImage
Major surface antigen p30
F, G
254Toxoplasma gondiiMutation(s): 0 
UniProt
Find proteins for P13664 (Toxoplasma gondii)
Explore P13664 
Go to UniProtKB:  P13664
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UniProt GroupP13664
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.10 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.241 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 71.034α = 90
b = 198.285β = 89.97
c = 128.366γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
CNSrefinement
PDB_EXTRACTdata extraction
AMoREphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2005-12-27
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.3: 2017-10-11
    Changes: Refinement description
  • Version 1.4: 2018-01-03
    Changes: Structure summary
  • Version 1.5: 2019-12-04
    Changes: Advisory, Derived calculations
  • Version 1.6: 2023-10-25
    Changes: Data collection, Database references, Derived calculations, Refinement description