Vibrio cholerae serotype O1 (strain ATCC 39315 / El Tor Inaba N

Cholera toxin is protein complex secreted by the bacterium Vibrio cholerae. It is responsible for the massive, watery diarrhea characteristic of cholera infection. The B subunit of cholera toxin (CtxB) binds to a GM1-ganglioside receptor, a ubiquitous glycolipid cell surface receptor. This binding is widely accepted to initiate toxin action by triggering uptake and delivery of the toxin A subunit into cells. The beta chain has no toxic activity by itself. The holotoxin consists of a pentameric ring of B subunits whose central pore is occupied by the A subunit. The A subunit contains two chains, A1 and A2, linked by a disulfide bridge.