Required for vesicle-mediated transport. Catalyzes the fusion of transport vesicles within the Golgi cisternae. Is also required for transport from the endoplasmic reticulum to the Golgi stack. Seems to function as a fusion protein required for the delivery of cargo proteins to all compartments of the Golgi stack independent of vesicle origin (By similarity). Required for maintaining the normal morphology of the Golgi apparatus (PubMed:29398689). ATP + H2O = ADP + H(+) + phosphate Binds 1 Mg(2+) ion per subunit. Homohexamer (By similarity). Binds to SNARE-SNAP complexes to form 20S particles (Probable). Belongs to the AAA ATPase family.