Structural and functional role of threonine 112 in a superantigen Staphylococcus aureus enterotoxin B

J Biol Chem. 2002 Jan 25;277(4):2756-62. doi: 10.1074/jbc.M109369200. Epub 2001 Nov 9.


Bacterial superantigens are potent T-cell stimulatory protein molecules produced by Staphylococcus aureus and Streptococcus pyogenes. Their superantigenic activity can be attributed to their ability to cross-link major histocompatibility complex class II molecules with T-cell receptors (TCRs) to form a tri-molecular complex. Each superantigen is known to interact with a specific V(beta) element of TCR. Staphylococcal enterotoxin B (SEB, a superantigen), a primary cause of food poisoning, is also responsible for a significant percentage of non-menstrual associated toxic shock syndrome in patients with a variety of staphylococcal infections. Structural studies have elucidated a binding cavity on the toxin molecule essential for TCR binding. To understand the crucial residues involved in binding, mutagenesis analysis was performed. Our analysis suggest that mutation of a conserved residue Thr(112) to Ser (T112S) in the binding cavity induces a selective reduction in the affinity for binding one TCR V(beta) family and can be attributed to the structural differences in the native and mutant toxins. We present a detailed comparison of the mutant structure determined at 2.0 A with the previously reported native SEB and SEB-TCR V(beta) complex structures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / chemistry
  • Conserved Sequence
  • Crystallography, X-Ray
  • Enterotoxins / chemistry*
  • Flow Cytometry
  • Genes, MHC Class II
  • Humans
  • Major Histocompatibility Complex
  • Microscopy, Fluorescence
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutation
  • Protein Binding
  • Protein Structure, Secondary
  • Receptors, Antigen, T-Cell, alpha-beta / chemistry
  • Receptors, Antigen, T-Cell, alpha-beta / metabolism
  • T-Lymphocytes / metabolism
  • Threonine / chemistry*
  • Threonine / physiology*


  • Amino Acids
  • Enterotoxins
  • Receptors, Antigen, T-Cell, alpha-beta
  • Threonine
  • enterotoxin B, staphylococcal

Associated data

  • PDB/1GOZ