Accessory component of a P4-ATPase flippase complex which catalyzes the hydrolysis of ATP coupled to the transport of aminophospholipids from the outer to the inner leaflet of various membranes and ensures the maintenance of asymmetric distribution of phospholipids. Phospholipid translocation seems also to be implicated in vesicle formation and in uptake of lipid signaling molecules. The beta subunit may assist in binding of the phospholipid substrate. Required for the proper folding, assembly and ER to Golgi exit of the ATP8A2:TMEM30A flippase complex. Required for the formation of the ATP8A2, ATP8B1 and ATP8B2 P-type ATPAse intermediate phosphoenzymes (By similarity). Component of various P4-ATPase flippase complexes which consists of a catalytic alpha subunit and an accessory beta subunit. The N-terminal domain seems to play a role in the reaction cycle of the catalytic subunit such as ATP8A2. Belongs to the CDC50/LEM3 family.