This gene encodes a member of the soluble NSF attachment protein (SNAP) family. SNAP proteins play a critical role in the docking and fusion of vesicles to target membranes as part of the 20S NSF-SNAP-SNARE complex. The encoded protein plays a role in the completion of membrane fusion by mediating the interaction of N-ethylmaleimide-sensitive factor (NSF) with the vesicle-associated and membrane-associated SNAP receptor (SNARE) complex, and stimulating the ATPase activity of NSF. Alternatively spliced transcript variants have been observed for this gene. The 'SNARE hypothesis' is a model explaining the process of docking and fusion of vesicles to their target membranes. Once the 2 classes of SNAREs bind to each other, they form a complex that recruits the general elements of the fusion apparatus, namely NSF (N-ethylmaleimide-sensitive factor) and SNAPs (soluble NSF-attachment proteins), to the site of membrane fusion, thereby forming the 20S fusion complex. Alpha- and gamma-SNAP are found in a wide range of tissues and act synergistically in intra-Golgi transport. The sequence of the predicted 295-amino acid human protein encoded by NAPA shares 37%, 60%, and 67% identity with the sequences of yeast, Drosophila, and squid alpha-SNAP, respectively. Platelets contain some of the same proteins, including NSF, p115/TAP, alpha-SNAP (this protein), gamma-SNAP, and the t-SNAREs syntaxin-2 and syntaxin-4, that are used in many vesicular transport processes in other cell types.