Complex sentence: In each case, Botuliunum Neurotoxins cause functional damage to SNARE proteins, and by doing so, the toxin prevents synaptic vesicles from fusing to the synaptic membrane and releasing their neurotransmitters into the synaptic cleft.
Split into simpler sentences: In each case, Botuliunum Neurotoxins cause functional damage to SNARE proteins. By doing so, this prevents synaptic vesicles from fusing with the cellular synaptic membrane and releasing their neurotransmitters into the synaptic cleft.