SNAP25

Synaptosomal-associated protein 25 (SNAP-25) is a t-SNARE protein that is encoded by the SNAP25 gene in humans. SNAP-25 is a component of the trans-SNARE complex, which is proposed to account for the specificity of membrane fusion and to directly execute fusion by forming a tight complex that brings the synaptic vesicle and plasma membranes together.

Structure and function

SNAP-25, a Q-SNARE protein, is anchored to the cytosolic face of membranes via palmitoyl side chains covalently bound to cysteine amino acid residues in the middle of the molecule. This means that SNAP-25 does not contain a trans-membrane domain.

SNAP-25 has been identified in contributing two α-helices to the SNARE complex, a four-α-helix domain complex. The SNARE complex participates in vesicle fusion, which involves the docking and merging of a vesicle with the cell membrane to bring about an exocytotic event. Synaptobrevin, a protein that is a part of the vesicle-associated membrane protein (VAMP) family, and syntaxin-1 also help form the SNARE complex by each contributing one α-helix. SNAP-25 assembles with synaptobrevin and syntaxin-1 and the selective binding of these proteins enables vesicle docking and fusion to occur at the correct location.