Pertussis Toxin (islet-activating protein), a toxin originally isolated from Bordetella pertussis, has been shown to catalyze ADP-ribosylation of a protein in membrane preparation from rat C6 glioma cells. In addition, exposure of Chinese hamster ovary cells in culture to this compound has resulted in a clustered growth pattern response. Other experiments have shown Pertussis Toxin to block the ability of inhibitory hormones to reduce adenylate cyclase activity and enhance the ability of stimulatory hormones to activate the enzyme. Mechanistic studies have shown this toxin to consist of subunit A (active) promoter, which disrupts transmembrane signaling by ADP-ribosylating eukaryotic G-proteins, and B (binding) oligomer which helps the toxin bind to cells in vivo.