Q-SNAREs are members of the SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein (SNAP) receptor) family that mediate vesicle-fusion. SNAREs are cytoplasmic, membrane-anchored proteins that contain a 60 amino acid SNARE domain. Three Q-SNAREs domains from the target membrane and one R-SNARE domain from the vesicle interact to form a four four-helix bundle that pulls the two membranes in close proximity and promotes fusion. After fusion, the complexes are dissembled by NSF (N-ethylmaleimide-sensitive factor) and SNAPs (Soluble NSF Attachment Proteins). Q-SNAREs are named from their contribution of a conserved glutamine (Q) residue to the helix bundle. Q SNARE domains are designated a, b or c, depending on their position within the helix bundle. (Adapted from PMID:15893389 and FBrf0216182).