Catalytic component of a P4-ATPase flippase complex which catalyzes the hydrolysis of ATP coupled to the transport of aminophospholipids, phosphatidylserines (PS) and phosphatidylethanolamines (PE), from the outer to the inner leaflet of intracellular membranes. May contribute to the maintenance of membrane lipid asymmetry in endosome compartment. Appears to play a role in the subnuclear trafficking of transcription factors with RING motifs. ATP + H2O + phospholipidSide 1 = ADP + phosphate + phospholipidSide 2. a 1,2-diacyl-sn-glycero-3-phospho-L-serine(out) + ATP + H2O = a 1,2-diacyl-sn-glycero-3-phospho-L-serine(in) + ADP + H(+) + phosphate a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(out) + ATP + H2O = a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(in) + ADP + H(+) + phosphate Component of a P4-ATPase flippase complex which consists of a catalytic alpha subunit ATP11B and an accessory beta subunit TMEM30A. Interacts with HLTF (via the RING-finger). Exit from the endoplasmic reticulum requires the presence of TMEM30A, but not TMEM30B. In the presence of TMEM30A, mainly located in recycling endosomes. Ubiquitously expressed. Up-regulated in endometrium upon stimulation with hormones, progesterone and prolactin. Is missing the sequence which constitutes transmembrane helix 4 and thus has an altered transmembrane architecture compared to isoform 1. The long domain (amino acids 352-868), which is normally cytoplasmic, extends into the nucleoplasm. This isoform is unique to rabbit. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IV subfamily.