SNARE proteins (an acronym derived from "SNAP (Soluble NSF Attachment Protein) REceptor") are a large protein superfamily consisting of more than 60 members in yeast and mammalian cells. The primary role of SNARE proteins is to mediate vesicle fusion, that is, the fusion of vesicles with their target membrane bound compartments (such as a lysosome). The best studied SNAREs are those that mediate docking of synaptic vesicles with the presynaptic membrane in neurons. These SNAREs are the targets of the bacterial neurotoxins responsible for botulism and tetanus.