Alpha-helix and beta-barrel pore-forming toxins (leucocidins, alpha-, gamma-, and delta-cytolysins) of Staphylococcus aureus

Abstract

Among more than 40 peptidic toxins that can be secreted by Staphylococcus aureus, pore-forming toxins (PFT) constitute one of the most important groups besides staphylococcal super antigens. This group of toxins is both diverse and multiple among those toxins secreted by this bacterium. Staphylococcal pore-forming toxins are divided into two subgroups comprised of those with alpha-helical structures and those rich in beta-strand sequences. Delta-hemolysin is one example of an alpha-helix structured toxin, while beta-sheetrich PFT can be further divided into two subfamilies of a homo-oligomeric toxin, alpha-hemolysin and heterooligomeric bicomponent leucotoxins. This chapter deals with the most recent findings with regards to these two groups of toxin. The different beta-barrel PFTs provide biological activity toward the wide variety of human blood cells, and several encoding genes can be genetically maintained in a single isolate, thus enhancing the leucotoxin combinations. This variety might constitute a benefit to the bacteria to escape the immune memory by the preservation of the biological activity of certain toxins at least. These toxins certainly constitute interesting toolsfor the bacteria to acquire the bulk of nutrients after cell lysis. © 2006 Elsevier Inc. All rights reserved.