Abstract
Clostridium botulinum type B neurotoxin cleaves VAMP(vesicle−associated membrane protein)/synaptobrevin into two fragments, which results in inhibition of neurotransmitter release.The induced fragment did not react to the antibody raised against the synthetic peptide of the amino−terminal 20 residues of VAMP−2, suggesting that the toxin treatment has caused antigenical alteration in the amino−terminal region of VAMP−2.In rat brain synaptosomes, type B neurotoxin was reduced presumably with sulfhydryls in the membrane and detected in the synaptic vesicle fraction which involved the degradation of VAMP−2 and the inhibition of neurotransmitter release.The light chain in a free form was present in the cytosol fraction.These findings suggest a possibility that type B neurotoxin endocytoses into synaptic vesicles by the recycling pathway and the light chain is penetrable through synaptic vesicle membrane.However, the amount of type B neurotoxin entrapped into synaptic vesicles appears to be extremely small, which may be attributed to a lower sensitivity of the toxin to brain synaptosomes than to peripheral nerve endings.
