The VAMP-4 (vesicle-associated membrane protein 4) protein belongs to the R-SNARE subgroup of SNAREs and interacts with syntaxin 16 (Qa), Vti1a (Qb) and syntaxin 6 (Qc). This complex plays a role in maintenance of Golgi ribbon structure and normal retrograde trafficking from the early endosome to the trans-Golgi network (TGN). SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins contain coiled-coil helices (called SNARE motifs) which mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complex mediates membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle. Their SNARE motifs form twisted and parallel heterotetrameric helix bundles.
Jiyao W et al.(2023). "The conserved domain database in 2023.",