Amisyn is a mostly cytosolic protein related to Tomosyn which plays an important role in SNARE complex assembly. Amisyn contains a v-SNARE coiled coil homology domain that binds to Syntaxin 1A and weakly to Syntaxin 4. Three isoforms exist for Amisyn. Isoform 1 is the full length protein, isoform 2 has a different amino acid sequence between residues 204-210 and isoform 3 is missing amino acids 1-102 and contains a different sequence for amino acids 103-150. Amisyn lacks a transmembrane domain and therefore is unable to assemble into a functional, membrane-anchored SNARE complex. This suggests that Amisyn may instead be acting to maintain SNARE conformation and facilitate the binding of VAMP-2. Amisyn can inhibit exocytosis independent of Syntaxin binding.