Superantigens SPEA and SMEZ do not affect secretome expression in Streptococcus pyogenes

The superantigens, toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxin B (SEB), were recently reported to repress global exoprotein synthesis in Staphylococcus aureus. To investigate if this phenomenon could be observed in a different Gram-positive pathogen, the effects of two major Streptococcus pyogenes superantigens on streptococcal secretome expression were examined. Using mutagenesis and genetic complementation, we demonstrated that neither streptococcal pyrogenic exotoxin A (SPEA) nor streptococcal mitogenic exotoxin Z (SMEZ) had any consistent effect on global protein expression or on transcription of genes encoding the secreted exoproteins, DNase B, SPEB and SPEG. In S. pyogenes, superantigen production does not appear to have a major regulatory role.