AFFINITY CHROMATOGRAPHY OF TETANUS TOXIN, TETANUS TOXOID, AND BOTULINUM-A TOXIN ON SYNAPTOSOMES, AND DIFFERENTIATION OF THEIR ACCEPTORS

125I-labeled tetanus toxin and 125I-labeled botulinum A neurotoxin are specifically bound to brain synaptosomes. To discriminate between active toxin and inactive admixtures present in the starting material or arising during iodination, synaptosome columns were prepared using bromacetylcellulose and/or kieselgur (Celite) as carriers. Both columns adsorb the toxins from low ionic strength medium and release them if the pH and ionic strength are raised. Botulinum toxin was eluted with lower ionic strength than tetanus toxin and could be freed from nontoxic admixtures. Affinity chromatography disclosed partially toxoided tetanus toxin in labeled and unlabeled toxin samples. High concentrations of formaldehyde (0.5%) destroyed toxicity and affinity to the synaptosomes of tetanus toxin. Low concentrations of formaldehyde (0.05%) yielded a derivative of low toxicity which was less firmly bound to synaptosomes. Tetanus and botulinum toxin differ by their acceptors. Unlabeled botulinum toxin is unable to compete with labeled tetanus toxin; unlabeled tetanus toxin slightly competes with botulinum toxin. Both labeled toxins display anomalous binding behavior; they cannot be displaced completely even with a large excess of unlabeled toxin.