SNAP-25, a membrane-associated protein of the nerve terminal, is specifically cleaved by botulinum neurotoxins serotypes A and E, which cause human and animal botulism by blocking neurotransmitter release at the neuromuscular junction. Here we show that these two metallo-endopeptidase toxins cleave SNAP-25 at two distinct carboxyl-terminal sites. Serotype A catalyses the hydrolysis of the Gln197-Arg198 peptide bond, while serotype E cleaves the Arg180-Ile181 peptide linkage. These results indicate that the carboxyl-terminal region of SNAP-25 plays a crucial role in the multi-protein complex that mediates vesicle docking and fusion at the nerve terminal.
