title: Transbilayer movement of phosphatidylserine in nonhuman erythrocytes: evidence that the aminophospholipid transporter is a ubiquitous membrane protein.
abstract: A 31-32-kDa integral membrane protein has been previously identified in erythrocytes as the protein most likely to be responsible for the transbilayer movement of phosphatidylserine (PS) [Connor & Schroit (1988) Biochemistry 27, 848-851]. Using similar techniques, we have identified analogous proteins of identical molecular weights in bovine, equine, ovine, porcine, canine, caprine, and rhesus red blood cells. Similar to human red blood cells, all of the mammalian cells were able to specifically transport an exogenously supplied fluorescent PS analogue from their outer-to-inner membrane leaflet. In addition, transport could be reversibly inhibited with the sulfhydryl-specific inhibitor pyridyldithioethylamine (PDA). PDA-sensitive PS transport was also observed in nucleated human and murine cell lines. Analysis of isolated plasma membranes from 125I-PDA-labeled cells revealed marked labeling of a 32,000-Da component. Attempts to inhibit PS transport by treating the cells with proteases, lectins, or antibody suggested that the 32-kDa polypeptide is an integral membrane protein that does not contain sites critical to its function at the cell surface.
authors.affiliation: Department of Cell Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: J
authors.initials: J
authors.lastname: Connor
authors.forename: A J
authors.initials: AJ
authors.lastname: Schroit
mesh_terms: D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D004220:Disulfides / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005453:Fluorescence; D006801:Humans; D008051:Lipid Bilayers / Q000493:pharmacokinetics; D008565:Membrane Proteins / Q000378:metabolism*; D010718:Phosphatidylserines / Q000493:pharmacokinetics*; D049294:Phospholipid Transfer Proteins; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits
chemical_list: D002352:Carrier Proteins; D004220:Disulfides; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010718:Phosphatidylserines; D049294:Phospholipid Transfer Proteins; D011725:Pyridines; C055639:pyridyldithioethylamine