Involved in the transport of biosynthetic membrane proteins from the prevacuolar/endosomal compartment to the vacuole. Required for multivesicular body (MVB) protein sorting. Catalyzes the ATP-dependent dissociation of class E VPS proteins from endosomal membranes, such as the disassembly of the ESCRT-III complex. Monomer or homodimer (in nucleotide-free form). Decamer, dodecamer or tetradecamer of two stacked respective homooligomeric rings (when bound to ATP); the dodecameric form seems to be predominant. Interacts with VPS20. Interacts with VTA1; the interaction requires the dimeric structure of VTA1; 6 homodimers of VTA1 appear to associate with the dodecameric VSP4 complex. Interacts with DID2. Interacts with DID4. Interacts with IST1; IST1 competes with VTA1 for binding with VPS4. Present with 5350 molecules/cell in log phase SD medium. Belongs to the AAA ATPase family.