Required for retention of late Golgi membrane proteins. Component of the retrieval machinery that functions by direct interaction with the cytosolic tails of certain TGN membrane proteins during the sorting/budding process at the prevacuolar compartment. Binds phosphatidylinositol 3-phosphate (PtdIns(P3)). Monomer. Interacts with RBD2, YIF1, YIP1 and YIP5. Mainly cytoplasmic. A minor amount associates with membranes. Belongs to the sorting nexin family.