Submitted to: Genbank
Publication Type: Other
Publication Acceptance Date: 2/7/2017
Publication Date: N/A
Technical Abstract: Clostridium perfringens (CP) is ubiquitous in the nature, and a normal inhabitant in the intestinal tracts of animals and humans. However, pathogenic CP is also a causative agent of poultry disease necrotic enteritis (NE). Clostridium perfringens alpha toxin is a toxin produced by the bacterium Clostridium perfringens (C. perfringens) and is responsible for gas gangrene and myonecrosis in infected tissues. The toxin also possesses hemolytic activity.The alpha toxin is a zinc metallophospholipase, requiring zinc for activation. First, the toxin binds to a binding site on the cell surface. The C-terminal C2-like PLAT domain binds calcium and allows the toxin to bind to the phospholipid head-groups on the cell surface. The C-terminal domain enters the phospholipid bilayer. The N-terminal domain has phospholipase activity. This property allows hydrolysis of phospholipids such as phosphatidyl choline, mimicking endogenous phospholipase C. The hydrolysis of phosphatidyl choline produces diacylglycerol, which activates a variety of second messenger pathways. The end-result includes activation of arachidonic acid pathway and production of thromboxane A2, production of IL-8, platelet-activating factor, and several intercellular adhesion molecules. These actions combine to cause edema due to increased vascular permeability. The gene encoding the a-(cpa) is present in all strains of Clostridium perfringens, and the purified a-toxin has been shown to be a zinc-containing phospholipase C enzyme, which is preferentially active towards phosphatidylcholine and sphingomyelin. The a-toxin is haemolytic as a result if its ability to hydrolyse cell membrane phospholipids and this activity distinguishes it from many other related zinc-metallophospholipases C. Recent studies have shown that the a-toxin is the major virulence determinant in cases of gas gangrene, and the toxin might play a role in several other diseases of animals and man as diverse as necrotic enteritis in chickens and Crohn's disease in man. In gas gangrene the toxin appears to have three major roles in the pathogenesis of disease. First, it is able to cause mistrafficking of neutrophils, such that they do not enter infected tissues. Second, the toxin is able to cause vaso-constriction and platelet aggregation which might reduce the blood supply to infected tissues. Finally, the toxin is able to detrimentally modulate host cell metabolism by activating the arachidonic acid cascade and protein kinase C. The molecular structure of the a-toxin reveals a two domain protein. The amino-terminal domain contains the phospholipase C active site which contains zinc ions. The carboxy-terminal domain is a paralogue of lipid binding domains found in eukaryotes and appears to bind phospholipids in a calcium-dependent manner. Immunisation with the non-toxic carboxyterminal domain induces protection against the a-toxin and gas gangrene and this polypeptide might be exploited as a vaccine. Other workers have exploited the entire toxin as the basis of an anti-tumour system.