title: Direct visualization of botulinum neurotoxin-induced channels in phospholipid vesicles.
abstract: The seven botulinum neurotoxin (NT) serotypes produced by strains of Clostridium botulinum inhibit neurotransmitter release from synaptic vesicles. Neurotoxin is synthesized as a roughly 150K single-chain protein. Proteolysis produces two fragments, the 50K L-chain and 100K H-chain, that remain linked by a disulphide bond. Intoxication involves membrane attachment by the C-terminal half of the H-chain, endocytotic/lysosomal internalization, vesicle channel formation mediated by the 50K N-terminal half of the H-chain at low pH, and finally blockade of synaptic vesicle fusion after the L-chain reaches the cytosol. We report here the visualization of the neurotoxin-membrane complex by electron cryomicroscopy and image processing. Three-dimensional reconstructions show the neurotoxin bound to the exterior of ganglioside/PC lipid vesicles and show channels entirely perforating the vesicle wall. Each channel appears to arise from the interaction of four neurotoxin molecules.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: M F
authors.initials: MF
authors.lastname: Schmid
authors.forename: J P
authors.initials: JP
authors.lastname: Robinson
authors.forename: B R
authors.initials: BR
authors.lastname: DasGupta
mesh_terms: D001905:Botulinum Toxins / Q000494:pharmacology*; D005732:Gangliosides; D007091:Image Processing, Computer-Assisted; D007473:Ion Channels / Q000648:ultrastructure*; D008051:Lipid Bilayers; D010743:Phospholipids
chemical_list: D005732:Gangliosides; D007473:Ion Channels; D008051:Lipid Bilayers; D010743:Phospholipids; D001905:Botulinum Toxins