Phospholipid scramblase involved in lipid homeostasis and membrane dynamics processes (By similarity). Required for autophagosome formation: participates in early stages of autophagosome biogenesis at the endoplasmic reticulum (ER) membrane by reequilibrating the leaflets of the ER as lipids are extracted (By similarity). In addition to autophagy, involved in other processes in which phospholipid scramblase activity is required (PubMed:18550798). a 1,2-diacyl-sn-glycero-3-phospho-L-serine(in) = a 1,2-diacyl-sn-glycero-3-phospho-L-serine(out) cholesterol(in) = cholesterol(out) a 1,2-diacyl-sn-glycero-3-phosphocholine(in) = a 1,2-diacyl-sn-glycero-3-phosphocholine(out) a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(in) = a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(out) Mutant cells display defects in the protein secretory pathway and in organelle biogenesis, and are deficient in their ability to initiate development upon starvation. The contractile vacuole, which is necessary to survive under hyperosmotic conditions, is non-functional in mutant cells. Belongs to the VMP1 family.