SNARE complex can mediate vesicle fusion between two membranes. In neuronal SNAREs, synaptobrevin, syntaxin and SNAP-25 contribute to the SNARE motifs (60-70 amino acids): one from each of synaptobrevin and syntaxin while two from SNAP-25 to form a four-helix bundle. In forming the zero ionic layer, synaptobrevin located in the synaptic vesicle contributes a glutamine (Q).while syntaxinor SNAP-25 contribute an arginine (R).Based on this, SNAREs can be divided into two types, R-SNAREs and Q-SNAREs. Q-SNAREs can be further classified into three subgroups, Qa, Qb and Qc.