Figure 1.

Historical hypothesized role of SNAREs in membrane trafficking. (A) The synaptic vesicle protein synaptotagmin was found to interact with the plasma membrane protein syntaxin, which also interacts with Ca⁺⁺ channels. (B) Trans-SNARE complexes dock vesicles and provide a scaffold for the assembly of the fusion apparatus. (C) Parallel alignment of SNARES forces membranes into close apposition. (D) Current hypothesis that SNARE complex formation is regulated by proteins such as n-sec1. Membrane fusion occurs in concert with trans-SNARE complex formation. α-SNAP and NSF then break apart cis-SNARE complexes to reset the system for another round of fusion.