Crystallographic and mutational data show that the streptococcal pyrogenic exotoxin J can use a common binding surface for T-cell receptor binding and dimerization.

The protein toxins known as superantigens (SAgs), which are expressed primarily by the pathogenic bacteria Staphylococcus aureus and Streptococcus pyogenes, are highly potent immunotoxins with the ability to cause serious human disease. These SAgs share a conserved fold but quite varied activities. In addition to their common role of cross-linking T-cell receptors (TCRs) and major histocompatibility complex class II (MHC-II) molecules, some SAgs can cross-link MHC-II, using diverse mechanisms.

Identification & characterisation of the two novel streptococcal pyrogenic exotoxins SPE-L & SPE-M.

Background & Objectives: The streptococcal pyrogenic exotoxins (SPEs) are produced by Streptococcus pyogenes and belong to the family of bacterial superantigens, a group of highly mitogenic proteins. The aim of this study was to search unfinished streptococcal genomes for novel superantigens, to generate recombinant proteins from potential open reading frames (ORFs) and to analyse them for superantigen activity.

Methods: The microbial genome database was searched using a TBLASTN search programme.

Two novel superantigens found in both group A and group C Streptococcus.

Two novel streptococcal superantigen genes (speL(Se) and speM(Se)) were identified from the Streptococcus equi genome database at the Sanger Center. Genotyping of 8 S. equi isolates and 40 Streptococcus pyogenes isolates resulted in the detection of the orthologous genes speL and speM in a restricted number of S.