Dear Editor,Phospholipid molecules are unevenly distributed in membrane bilayers of eukaryotic cells.Phosphatidylethanolamine (PE) and phosphatidylserine (PS) are concentrated in the cytoplasmic leaflet,whereas phosphatidylcholine (PC) is enriched in the exoplasmic leaflet (lumenal or extracellular leaflet) (van Meer et al.2008).Type 4 P-type ATPases (P4-ATPases) are the phospholipid flippases which move specific lipids from the exoplasmic leaflet to the cytoplasmic leaflet.P4-ATPases belong to the P-type ATPase family.P4-ATPases are conserved in eukaryotes.