6lkn
From Proteopedia
Crystal structure of ATP11C-CDC50A in PtdSer-bound E2P state
Structural highlights
DiseaseAT11C_HUMAN The disease is caused by mutations affecting the gene represented in this entry. FunctionAT11C_HUMAN Catalytic 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. In the cell membrane of erythrocytes, it is required to maintain phosphatidylserine (PS) in the inner leaflet preventing its exposure on the surface. This asymmetric distribution is critical for the survival of erythrocytes in circulation since externalized PS is a phagocytic signal for splenic macrophages (PubMed:26944472). Phospholipid translocation seems also to be implicated in vesicle formation and in uptake of lipid signaling molecules (By similarity). Required for B cell differentiation past the pro-B cell stage (By similarity). Seems to mediate PS flipping in pro-B cells (By similarity). May be involved in the transport of cholestatic bile acids (By similarity).[UniProtKB:Q9QZW0][1] Publication Abstract from PubMedATP11C, a member of the P4-ATPase flippase, translocates phosphatidylserine from the outer to the inner plasma membrane leaflet, and maintains the asymmetric distribution of phosphatidylserine in the living cell. We present the crystal structures of a human plasma membrane flippase, ATP11C-CDC50A complex, in a stabilized E2P conformation. The structure revealed a deep longitudinal crevice along transmembrane helices continuing from the cell surface to the phospholipid occlusion site in the middle of the membrane. We observed that the extension of the crevice on the exoplasmic side is open, and the complex is therefore in an outward-open E2P state, similar to a recently reported cryo-EM structure of yeast flippase Drs2p-Cdc50p complex. We noted extra densities, most likely bound phosphatidylserines, in the crevice and in its extension to the extracellular side. One was close to the phosphatidylserine occlusion site as previously reported for the human ATP8A1-CDC50A complex, and the other in a cavity at the surface of the exoplasmic leaflet of the bilayer. Substitutions in either of the binding sites or along the path between them impaired specific ATPase and transport activities. These results provide evidence that the observed crevice is the conduit along which phosphatidylserine traverses from the outer leaflet to its occlusion site in the membrane and suggest that the exoplasmic cavity is important for phospholipid recognition. They also yield insights into how phosphatidylserine is incorporated from the outer leaflet of the plasma membrane into the transmembrane. Crystal structure of a human plasma membrane phospholipid flippase.,Nakanishi H, Irie K, Segawa K, Hasegawa K, Fujiyoshi Y, Nagata S, Abe K J Biol Chem. 2020 Jun 3. pii: RA120.014144. doi: 10.1074/jbc.RA120.014144. PMID:32493773[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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