Class E VPS protein involved in concentration and sorting of cargo proteins of the multivesicular body (MVB) for incorporation into intralumenal vesicles. Fusion between endosomes and the vacuole will then target the cargo proteins to the vacuolar lumen (Probable). Associates with FREE1 and ELC to perform function in the ESCRT-I complex. Binds ubiquitin in vitro (PubMed:26902184). Plays a role in the biogenesis of vacuole and multivesicular bodies (MVBs) (PubMed:26342016, PubMed:26324913). Required for the endosomal location of AMSH3 (PubMed:26324913). Mediates high-affinity phosphate transporter trafficking to maintain phosphate homeostasis. Regulates vacuolar degradation of PHT1-1 (PubMed:26342016). Homodimer (PubMed:26342016). Interacts with AMSH3 (PubMed:26324913). Interacts with VPS32.1/SNF7B and VPS32.2/SNF7A (PubMed:22639582, PubMed:26342016). Interacts with ELC/VPS23A (PubMed:26902184). Seedlings lethality. Severe vacuole biogenesis defects.