The lysosomal VAMP8 (vesicle-associated membrane protein 8, also called endobrevin) protein belongs to the R-SNARE subgroup of SNAREs and interacts with STX17 (Qa) and SNAP29 (Qb/Qc). The complex plays a role in autophagosome-lysosome fusion via regulating the transport from early endosomes to multivesicular bodies. Autophagosome transports cytoplasmic materials including cytoplasmic proteins, glycogen, lipids, organelles, and invading bacteria to the lysosome for degradation. 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.",