Channels formed by botulinum, tetanus, and diphtheria toxins in planar lipid bilayers: relevance to translocation of proteins across membranes.

Abstract

The H chains of both botulinum neurotoxin type B and tetanus toxin form channels in planar bilayer membranes. These channels have pH-dependent and voltage-dependent properties that are remarkably similar to those previously described for diphtheria toxin. Selectivity experiments with anions and cations show that the channels formed by the H chains of all 3 toxins are large; thus, these channels could serve as tunnel proteins for translocation of active peptide fragments. The hypothesis that the active fragments of botulinum neurotoxin and tetanus toxin, like that of diphtheria toxin, are translocated across the membranes of acidic vesicles is supported.