SNAP23(Synaptosomal-Associated Protein, 23-KD), also called SNAP23A, is a protein that in humans is encoded by the SNAP23 gene. The SNAP23 gene has 8 exons, with the initiation codon located in exon 2. The SNAP23 gene is mapped on 15q15.1-q15.2. The SNAP23 cDNA encodes a 211-amino acid polypeptide with a predicted mass of 23 kD. Its amino acid sequence is 59% identical to that of SNAP25. Northern blot analysis revealed that SNAP23 is ubiquitously expressed. SNAP23 is able to bind to multiple syntaxins as well as to multiple vesicle-associated membrane proteins. After relocation, SNAP23 is required for exocytosis, implying a crucial role in promoting membrane fusion. TIVAMP-containing vesicles were concentrated in the apical domain of epithelial cells. STX3A and SNAP23 were codistributed at the apical plasma membrane, where they formed N-ethyl maleimide-dependent SNARE complexes with TIVAMP and cellubrevin. SNAP23 is structurally and functionally similar to SNAP25 and binds tightly to multiple syntaxins and synaptobrevins/VAMPs. It is an essential component of the high affinity receptor for the general membrane fusion machinery and is an important regulator of transport vesicle docking and fusion.