The Cholesterol-dependent Cytolysins and Clostridium septicum α-Toxin; Pore Forming Toxins of the Clostridia
Eileen M. Hotze and Rodney K. Tweten
from: Clostridia: Molecular Biology in the Post-genomic Era (Edited by: Holger Brüggemann and Gerhard Gottschalk). Caister Academic Press, U.K. (2009)
Two classes of pore-forming toxins of the clostridia are represented by the cholesterol-dependent cytolysins (CDCs) and the Clostridium septicum α-toxin. The CDCs are found in a wide variety of clostridial species, but are also found in many species from other Gram-positive genera. As a result, various CDCs have evolved specific traits that appear to enhance their ability to complement the pathogenic mechanism of a specific bacterial species. In contrast, closely related toxins to C. septicum α-toxin (AT) have not been found in other species of the clostridia, although C. perfringens epsilon toxin appears to be distantly related. Remarkably, distant relatives of AT have been found in species of Gram-negative bacteria as well as certain species of mushrooms and the enterolobin tree seed. Although the CDCs appear to be restricted to Gram-positive bacterial pathogens it has recently been shown that the unusual protein fold of their membrane-penetrating domain is present in proteins of the eukaryotic complement membrane attack complex. Both toxins penetrate the membrane by the use of a β-barrel pore but differ significantly in their pore-forming mechanisms. The contribution of both classes of toxins to disease is not yet well understood for the clostridia. It is clear that they play important, but likely different roles in clostridial disease read more ...