Cooperative action of the light chain of tetanus toxin and the heavy chain of botulinum toxin type A on the transmitter release of mammalian motor endplates.

Purified heavy chain of botulinum toxin type A and light chain of tetanus toxin were combined to form a chimeric toxin. It was active on the mouse phrenic nerve-hemidiaphragm with a potency 6 times higher than that of native tetanus toxin. Electrophysiological data from poisoned neuromuscular junctions revealed that the pattern of nerve-evoked and spontaneous transmitter release was equivalent to that seen with tetanus toxin i.e. asynchronous release, and did not resemble that after botulinum toxin type A poisoning. We conclude that the light chain of tetanus toxin alone is responsible for the characteristic effects on spontaneous and nerve-evoked transmitter release of the native toxin and that these properties can be introduced into a new, more potent complex with the heavy chain of botulinum toxin A.