Botulinum neurotoxin type G proteolyses the Ala81-Ala82 bond of rat synaptobrevin 2

Tetanus toxin and the botulinum neurotoxins types A to F inhibit neurotransmitter release from presynaptic nerve endings by selectively proteolysing the synaptic proteins synaptobrevin, syntaxin, or SNAP-25. Here, we show that botulinum toxin type G cleaves rat synaptobrevin 2 between Ala81 and Ala82, a peptide bond that differs from those attacked by tetanus toxin and the botulinal toxins types B, D, and F. Synaptobrevin isoforms carrying a Gly in the P1 position are poor substrates. Analyses of N-terminal deletion mutants of rat synaptobrevin 2 showed that a substrate starting at Leu54 is cleaved efficiently, whereas substrates beginning at Leu60 or Phe77 are cleaved partially or not at all, respectively.