Bacterial type AB₅ enterotoxins--structure, function and mechanism of action

One of the main factors causing bacterial diarrhea are AB₅ enterotoxins. This group is divided into four families: pertussis toxin, cholera toxin, shiga toxin and subtilase cytotoxin. In this review we will describe the activity, structure and function of the cholera and shiga toxin families. The AB₅ enterotoxins contain a catalytic subunit A and pentameric subunit B, which binds to the cell surface within lipid rafts. The cholera toxin family cause the constitutive activation of Gsa protein, which results in cAMP production, an opening of the chloride channels and releases chloride ions into the lumen of the small intestine. In contrast, the shiga toxin family has a cytotoxic effect on epithelial cells. It can inhibit protein synthesis leading to cell death. Although AB₅ has a toxic activity, the B₅ subunits have a significant potential as a transporter for proteins with anticancer activity and as a tool for the visualization of lipid rafts and cancer cells.