Heat-stable enterotoxins are secretory peptides produced by some bacterial strains. These peptides keep their 3D structure and remain active at 100^oC. Different STs recognize distinct receptors on the cell surface and thereby affect different intracellular signaling pathways. For example, STa enterotoxins bind and activate membrane-bound guanylate cyclase, which leads to the intracellular accumulation of cyclic GMP and downstream effects on several signaling pathways. These events lead to the loss of electrolytes and water from intestinal cells.

Members of heat-stable enterotoxin B family assume a helical secondary structure, with two alpha helices forming a disulfide cross-linked alpha-helical hairpin. The disulfide bonds are crucial for the toxic activity of the protein, and are required for maintenance of the tertiary structure, and subsequent interaction with the particulate form of guanylate cyclase, increasing cyclic GMP levels within the host intestinal epithelial cells.

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