Neurotransmitter release is blocked intracellularly by botulinum neurotoxin, and this requires uptake of both toxin polypeptides by a process mediated by larger chain. - Poulain,B.; Taux,L.; Maisey,EA.; Walsworth,JD.; Mohan,PM.; Dolly,JO. (Proc Natl Acad Sci USA, 1988)