Channels formed in phospholipid bilayer membranes by diphtheria, tetanus, botulinum and anthrax toxin.

Diphtheria, tetanus, botulinum, and anthrax toxin are multipartate toxins, one of the domains of which is (or is presumed to be) an enzyme. Cell intoxication requires that the enzymatic portion gain access to the cytosol via endocytosis into an acidic vesicle compartment of the cell. Translocation of the enzyme across the vesicular membrane is dependent on the low pH of the vesicle and involves another domain of the toxin; for each of these toxins, that domain is capable of forming channels in phospholipid bilayer membranes. These channels are large (greater than 12 A diameter) and voltage-gated, and the pH conditions required for their formation in lipid bilayers are similar to those existing in acidic vesicles and required for cell intoxication.