[51] Nonspecific lipid transfer protein from rat and beef liver: Purification and properties

This chapter discusses the purification and properties of nonspecific lipid transfer protein from rat and beef liver. The nonspecific lipid transfer proteins accelerate the intermembrane transfer of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidic acid, phosphatidylglycerol, sphingomyelin, cholesterol, neutral glycosphingolipids, and gangliosides. The transfer proteins are useful tools for the study of the distribution and movement of phospholipids in artificial vesicles, microsomes, intact erythrocytes, and Semliki Forest virus and of cholesterol in the brush-border plasma membranes of the rabbit intestine. The assay of transfer activity is based on the ability of nonspecific lipid transfer proteins to accelerate the transfer of labeled phosphatidylethanolamine from phosphatidylethanolamine–phosphatidylcholinc small unilamellar vesicles to beef heart mitochondria. A trace of labeled triolein is included in the small unilamellar vesicles during preparation to correct for vesicle recovery. After the incubations, the mitochondria are pelleted and aliquots of the supernatants, containing the vesicles, are counted. A measure of the transfer activity is given by the decrease in the phosphatidylethanolamine/triolein ratio of the supernatants.