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The domain structure and functional relationships in the bacterial superantigen, SEB
J D Hayball1, R E O'Hehir, J R Lamb
1Department of Immunology, St. Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, UK.
Biological Chemistry Hoppe-Seyler
|May 1, 1995
Summary
Staphylococcal enterotoxin B (SEB) is a potent toxin that triggers T cells. Its amino-terminal domain is crucial for T cell stimulation, with specific residues essential for activity.
Area of Science:
- Immunology
- Microbial toxins
- Protein structure-function relationships
Background:
- Staphylococcal enterotoxin B (SEB) is a superantigen with potent toxicity.
- SEB interacts with T cell receptors (TcR) and MHC class II molecules.
- SEB triggers a subset of T cells expressing specific V beta gene products.
Purpose of the Study:
- To investigate the role of specific SEB domains in T cell stimulation.
- To identify the minimal mitogenic component of SEB.
- To analyze the impact of mutations on SEB's interaction with TcR and MHC class II.
Main Methods:
- Site-directed mutagenesis to create SEB variants.
- Assays to measure T cell mitogenicity.
- Analysis of SEB binding affinity to MHC class II molecules.
Main Results:
- The amino-terminal 138 residues of SEB are essential for human T cell stimulation.
- A mutant lacking residues 131-138 (SEB delta 131-138) retained mitogenic activity but altered TcR interaction.
- The disulfide loop is not essential for T cell recognition, and mutants showed reduced MHC class II binding affinity.
Conclusions:
- The amino-terminal domain of SEB is critical for its superantigen activity.
- Specific residues within this domain are vital for T cell receptor and MHC class II interactions.
- SEB's structure-toxicity relationship is complex, involving distinct domains for different functions.