Difference in hydrophobicity between botulinum type B activated and non-activated neurotoxins under low pH conditions.

We showed that botulinum type B activated neurotoxin with a di-chain structure became hydrophobic more quickly and extensively than did the non-activated toxin with a single-chain structure on low pH exposure. The activated toxin possessed 50-fold higher toxicity than did the non-activated type. The difference in the susceptibility to hydrophobic change may be one clue to answering the question of why the activated toxin possesses a higher toxicity than does the non-activated type.