Exotoxins of Staphylococcus aureus

Abstract

This article reviews the literature regarding the structure and function of two types of exotoxins expressed by Staphylococcus aureus, pyrogenic toxin superantigens (PTSAgs) and hemolysins. The molecular basis of PTSAg toxicity is presented in the context of two diseases known to be caused by these exotoxins: toxic shock syndrome and staphylococcal food poisoning. The family of staphylococcal PTSAgs presently includes toxic shock syndrome toxin-1 (TSST-1) and most of the staphylococcal enterotoxins (SEs) (SEA, SEB, SEC, SED, SEE, SEG, and SEH). As the name implies, the PTSAgs are multifunctional proteins that invariably exhibit lethal activity, pyrogenicity, superantigenicity, and the capacity to induce lethal hypersensitivity to endotoxin. Other properties exhibited by one or more staphylococcal PTSAgs include emetic activity (SEs) and penetration across mucosal barriers (TSST-1). A detailed review of the molecular mechanisms underlying the toxicity of the staphylococcal hemolysins is also presented.

FIG. 1

Ribbon diagram of TSST-1 in the standard view, showing both domains A and B.

FIG. 2

Ribbon diagram of the modeled structure of the MHC class II–TSST-1–TCR complex.

FIG. 3

Ribbon diagram of SEC3 in the standard view, showing both domains A and B.

FIG. 4

Representation of formation of the heptameric pore in a eukaryotic cell membrane by staphylococcal alpha-hemolysin. The rim domain of the toxin adheres to the membrane, and the intertwined stem regions are responsible for the formation of a pore, with an exclusionary radius of 14 Å.