Synaptic vesicle docking and fusion at release sites require the association of proteins on both vesicle and plasma membranes. Syntaxin interacts with synaptobrevin/VAMP and SNAP-25, constituting the SNARE core complex. This complex's formation comprises the minimal molecular requirement for membrane fusion in vitro. However, the Ca²⁺-triggered synaptic vesicle fusion with presynaptic plasma membrane can be regulated rapidly and tightly when the main SNARE intermediate is so stable. Some synaptic proteins, which regulate the accessibility of SNARE components by interacting with the individual SNARE proteins, might tightly control assembly of functional fusion machinery. Thus, the identification of regulators or molecular switches involved in the assembly of the fusion core complexes is critical for elucidating the molecular mechanisms underlying neurotransmitter release and synaptic plasticity.