Acta Pharmacologica Sinica 2006 September; 27 (9): 1238-1246; doi: 10.1111/j.1745-7254.2006.00372.x

Aim: To determine the structure factors that mediate the intoxication process of botulinum neurotoxin type A (BoNT/A).

Methods: Triton X-114 phase separation experiments and 1-anilino-8-naphthalene sulfonate binding assay were used to study the structural factor that corresponds to the hydrophobicity change of BoNT/A. In addition, sucrose density gradient centrifugation and a chemical crosslinking study were employed to determine the quaternary structure of BoNT/A.

Results: Our results demonstrated that in other than acidic conditions, the disulfide reduction is the structural factor that corresponds to the hydrophobicity change of BoNT/A. The quaternary structure of BoNT/A exists as a dimmer in acidic solution (pH 4.5), although the monomeric structure of BoNT/A was reported based on X-ray crystallography.

Conclusion: Disulfide bond reduction is critical for BoNT/A's channel formation and ability to cross endosome membranes. This result implies that compounds that block this disulfide bond reduction may serve as potential therapeutic agents for botulism.

Keywords: Clostridium botulinum; botulinum neuro-toxin A; hydrophobicity; phase partition