title: Intracellular phospholipid transfer and exchange.
abstract: The intracellular transfer of phospholipids in rat liver was studied. The factors affecting the transport and the role of phospholipid transfer proteins in this process were investigated. The procedure was based upon the labelling of microsomal phospholipids with either 14C or 32P, and incubation with unlabelled mitochondria in an in vitro system. The re-isolated mitochondria became labelled demonstrating an exchange of phospholipid between the two membranes. The transfer was stimulated by the addition of high-speed supernatant, was unaffected by the addition of ATP, but did not occur at 0 degrees C. Phospholipid transfer between liposomes and mitochondria was shown to occur, suggesting that the participation of natural membranes is not required for transfer to take place. The conditions required were found to be similar, and the high speed supernatant promoted transfer to the same extent as when labelled microsomes acted as the donor. The transfer activity of the high-speed supernatant was abolished by treatment with sulphydryl-blocking agents. Beef supernatant was adjusted to pH 5.1 and the activity remained in the supernatant. The pH 5.1 supernatant was applied to a Sephadex G-75 column and two active fractions were collected. The higher molecular weight fraction contained several proteins and stimulated the transfer of phosphatidylcholine and phosphatidylethanolamine. The lower molecular weight active fraction contained a protein which specifically stimulated the transfer of phosphatidylcholine.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D007700:Kinetics; D008081:Liposomes; D008099:Liver / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013696:Temperature
chemical_list: D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D011506:Proteins