Bilayers containing gangliosides develop channels when exposed to cholera toxin

Abstract

CHOLERA toxin, a protein of molecular weight 84,000, comprising five or six B and one A subunits, produces massive diarrhoea in man and other mammals by altering the transport of salt and water across the intestinal epithelium^1–4. These effects are mediated by a sequence of events leading to an increase in the concentration of cyclic AMP in the epithelial cells. The sequence involves binding of the toxin through its B subunits to specific receptors which seem to be the mono-sialoganglioside galactosyl-N-acetyl-galactosaminyl-(N-acetyl-neuraminyl)-galactosyl-glucosyl-ceramide (G_M1), and subsequent activation of adenyl cyclase^5–7. We report here experiments which show that cholera toxin reacts with lipid bilayers containing G_M1 to form channels which allow ions present in the aqueous solution to traverse the membrane.