The Pseudomonas exotoxin (or exotoxin A) is an exotoxin produced by Pseudomonas aeruginosa. Vibrio cholerae produces a similar protein called the Cholix toxin (Q5EK40). The Pseudomonas exotoxin (or exotoxin A) is an exotoxin produced by Pseudomonas aeruginosa. Vibrio cholerae produces a similar protein called the Cholix toxin (Q5EK40). It inhibits elongation factor-2. It does so by ADP-ribosylation of EF2 using NAD+. This then causes the elongation of polypeptides to cease. This mechanism is similar to that of diphtheria toxin. It has been investigated as a treatment for hepatitis B and cancer.