An exotoxin, produced by Vibrio cholerae and Vibrio eltor, thats leeds to the massive, watery diarrhea characteristic of cholera infection.

The cholera toxin is a member of the AB family of toxins. The function of the non-toxic B subunit is to assemble into a ring-shaped, homologous pentamer and to adhere to mem-brane receptors on the intestinal epithelial cell surface (GM1 gangliosides). The pathogenic effect stems from the A subunit. This is split into two domains, an anchor domain A2 and a toxic domain A1. The anchor domain binds the toxic A1 domain to the B subunit. Through a series of further intermediate activation steps, the A1 domain ultimately causes a massive secretion of chloride ions in the gut lumen, causing diarrhoea. It follows that the A1 subunit is toxic, but the B subunit is non-toxic.