– Cholera toxin is protein complex secreted by the bacterium Vibrio cholerae. It is responsible for the massive, watery diarrhea characteristic of cholera infection. Cholera enterotoxin subunit B (CTXB) pentameric ring directs the A subunit to its target by binding to the GM1 gangliosides present on the surface of the intestinal epithelial cells. It can bind five GM1 gangliosides. It has no toxic activity by itself.