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. ATP8A2:TMEM30A may be involved in regulation of neurite outgrowth, and, reconstituted to liposomes, predomiminantly transports phosphatidylserine (PS) and to a lesser extent phosphatidylethanolamine (PE). The ATP8A1:TMEM30A flippase complex seems to play a role in regulation of cell migration probably involving flippase-mediated translocation of phosphatidylethanolamine (PE) at the plasma membrane. Required for the formation of the ATP8A2, ATP8B1 and ATP8B2 P-type ATPAse intermediate phosphoenzymes. Involved in uptake of platelet-activating factor (PAF). Can also mediate the export of alpha subunits ATP8A1, ATP8B1, ATP8B2, ATP8B4, ATP10A, ATP10B, ATP10D, ATP11A, ATP11B and ATP11C from ER to other membrane localizations (By similarity). Component of various P4-ATPase flippase complexes which consists of a catalytic alpha subunit and an accessory beta subunit. Interacts with ATP8A1 to form a flippase complex; this complex forms an intermediate phosphoenzyme. Interacts with ATP8A2 to form a flippase complex (By similarity). TP8B1:TMEM30A and ATP8B2:TMEM30A flippase complexes have been shown to form intermediate phosphoenzymes in vitro. Interacts with alpha subunits ATP8A1, ATP8B1, ATP8B2, ATP8B4, ATP10A, ATP10B, ATP10D, ATP11A, ATP11B and ATP11C. The N-terminal domain seems to play a role in the reaction cycle of the catalytic subunit such as ATP8A2. N-glycosylated. Contains high mannose-type oligosaccharides (By similarity). Belongs to the CDC50/LEM3 family.