Evidence for direct binding of Clostridium botulinum type E derivative toxin and its fragments to gangliosides and free fatty acids.

Clostridium botulinum type E derivative toxin and its heavy chain bound to gangliosides GT1b, GD1a and GQ1b and saturated and unsaturated free fatty acids with chain lengths of 14-20 carbons. The L-H-1 fragment lacking the carboxyl-terminal portion of the heavy chain bound to free fatty acids but not to gangliosides. These observations led us to a new hypothesis on the mechanism of binding between botulinum toxin and gangliosides; the carboxyl-terminal portion (H-2 fragment) of the heavy chain binds to an oligosaccharide residue of gangliosides and then the amino-terminal portion (H-1 fragment) interacts with the hydrophobic portion of gangliosides consisting of fatty acids.