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Crystal structure of the superantigen staphylococcal enterotoxin type A
E M Schad1, I Zaitseva, V N Zaitsev
1Molecular Biophysics, Chemical Centre, Lund University.
The EMBO Journal
|July 17, 1995
Summary
Staphylococcal enterotoxin A (SEA) structure reveals a unique zinc-binding site crucial for its interaction with major histocompatibility complex (MHC) class II molecules, explaining its superantigen activity.
Area of Science:
- Immunology
- Structural Biology
- Protein Crystallography
Background:
- Staphylococcal enterotoxins are potent superantigens that activate T-lymphocytes by binding to MHC class II molecules.
- Understanding the structural basis of this interaction is key to comprehending their immunomodulatory effects.
Purpose of the Study:
- To determine the high-resolution crystal structure of staphylococcal enterotoxin type A (SEA).
- To identify structural features unique to SEA, particularly those involved in MHC class II binding.
Main Methods:
- X-ray crystallography was employed to determine the 3D structure of SEA.
- Multiple isomorphous replacement phasing was used to solve the crystal structure.
- The structure was refined to 1.9 Å resolution.
Main Results:
- The crystal structure of SEA (27 kDa monomer) was determined, revealing a two-domain structure with beta-barrel and beta-grasp motifs, similar to other enterotoxins.
- A unique Zn2+ coordination site involving Ser1, His187, His225, and Asp227 was identified.
- This Zn2+ site is implicated in the binding of SEA to MHC class II molecules.
Conclusions:
- SEA is the first structurally characterized Zn2+ binding enterotoxin.
- The identified Zn2+ coordination site provides novel insights into the molecular mechanisms of SEA-MHC class II interaction.
- This structural information can inform the development of strategies to modulate superantigen activity.