2ICI

Crystal Structure of Streptococcal Pyrogenic Exotoxin I


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.56 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.176 
  • R-Value Observed: 0.178 

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This is version 1.2 of the entry. See complete history


Literature

Crystal Structure of the Streptococcal Superantigen SpeI and Functional Role of a Novel Loop Domain in T Cell Activation by Group V Superantigens.

Brouillard, J.N.Gunther, S.Varma, A.K.Gryski, I.Herfst, C.A.Rahman, A.K.Leung, D.Y.Schlievert, P.M.Madrenas, J.Sundberg, E.J.McCormick, J.K.

(2007) J Mol Biol 367: 925-934

  • DOI: 10.1016/j.jmb.2007.01.024
  • Primary Citation of Related Structures:  
    2ICI

  • PubMed Abstract: 
  • Superantigens (SAgs) are potent microbial toxins that bind simultaneously to T cell receptors (TCRs) and class II major histocompatibility complex molecules, resulting in the activation and expansion of large T cell subsets and the onset of numerous ...

    Superantigens (SAgs) are potent microbial toxins that bind simultaneously to T cell receptors (TCRs) and class II major histocompatibility complex molecules, resulting in the activation and expansion of large T cell subsets and the onset of numerous human diseases. Within the bacterial SAg family, streptococcal pyrogenic exotoxin I (SpeI) has been classified as belonging to the group V SAg subclass, which are characterized by a unique, relatively conserved approximately 15 amino acid extension (amino acid residues 154 to 170 in SpeI; herein referred to as the alpha3-beta8 loop), absent in SAg groups I through IV. Here, we report the crystal structure of SpeI at 1.56 A resolution. Although the alpha3-beta8 loop in SpeI is several residues shorter than that of another group V SAg, staphylococcal enterotoxin serotype I, the C-terminal portions of these loops, which are located adjacent to the putative TCR binding site, are structurally similar. Mutagenesis and subsequent functional analysis of SpeI indicates that TCR beta-chains are likely engaged in a similar general orientation as other characterized SAgs. We show, however, that the alpha3-beta8 loop length, and the presence of key glycine residues, are necessary for optimal activation of T cells. Based on Vbeta-skewing analysis of human T cells activated with SpeI and structural models, we propose that the alpha3-beta8 loop is positioned to form productive intermolecular contacts with the TCR beta-chain, likely in framework region 3, and that these contacts are required for optimal TCR recognition by SpeI, and likely all other group V SAgs.


    Organizational Affiliation

    Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada N6A 5B8.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Exotoxin IA227Streptococcus pyogenesMutation(s): 6 
Gene Names: speI
Find proteins for Q1CQP3 (Streptococcus pyogenes serotype M12 (strain MGAS9429))
Explore Q1CQP3 
Go to UniProtKB:  Q1CQP3
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MG
Query on MG

Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Modified Residues  1 Unique
IDChainsTypeFormula2D DiagramParent
MSE
Query on MSE
AL-PEPTIDE LINKINGC5 H11 N O2 SeMET
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.56 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.176 
  • R-Value Observed: 0.178 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 30.864α = 90
b = 80.441β = 99.51
c = 43.054γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
PDB_EXTRACTdata extraction
HKL-2000data collection
HKL-2000data reduction
HKL-2000data scaling
SOLVEphasing

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2007-03-27
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance