N-ethylmaleimide-sensitive factor Attachment Protein Alpha, also known as SNAP-α, is a protein that is involved in the intra-cellular trafficking and fusing of vesicles to target membranes in cells.
The 'SNARE hypothesis' is a model explaining the process of docking and fusion of vesicles to their target membranes. According to this model, membrane proteins from the vesicle (v-SNAREs) and proteins from the target membrane (t-SNAREs) govern the specificity of vesicle targeting and docking through mutual recognition. 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. Platelet exocytosis uses a molecular mechanism similar to that used by other secretory cells, such as neurons, although the proteins used by the platelet and their modes of regulation may be quite different.
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