Cholera cytolysin cell toxin, molecular model. This is the Vibrio cholerae cytolysin (VCC) toxin from the bacterium that causes cholera. It is a pore-forming toxin (PFT) whose function is to bind to cell membranes and cause lysis (cell damage) leading to the death of the cell. This toxin is a heptameric structure, with seven subunits forming this circular structure. Cholera is a water-borne disease that causes diarrhoea and vomiting.