page_title: Cholera toxin
section_title: Structure
hierarchical_section_title: Cholera toxin / Structure
caption_attribution_description: English: Cholera toxin B pentamer, Vibrio cholerae
context_page_description: Cholera toxin is AB5 multimeric protein complex secreted by the bacterium Vibrio cholerae. CTX is responsible for the massive, watery diarrhea characteristic of cholera infection. It is a member of the Heat-labile enterotoxin family.
context_section_description: The cholera toxin is an oligomeric complex made up of six protein subunits: a single copy of the A subunit (part A, enzymatic, P01555), and five copies of the B subunit (part B, receptor binding, P01556), denoted as AB₅. Subunit B binds while subunit A activates the G protein which activates adenylate cyclase. The three-dimensional structure of the toxin was determined using X-ray crystallography by Zhang et al. in 1995.
  The five B subunits—each weighing 11 kDa, form a five-membered ring. The A subunit which is 28 kDa, has two important segments.  The A1 portion of the chain (CTA1) is a globular enzyme payload that ADP-ribosylates G proteins, while the A2 chain (CTA2) forms an extended alpha helix which sits snugly in the central pore of the B subunit ring.
  This structure is similar in shape, mechanism, and sequence to the heat-labile enterotoxin secreted by some strains of the Escherichia coli bacterium.
caption: Cholera toxin B pentamer, Vibrio cholerae.
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