The interactions of lysophosphatidylcholine with protein-containing liposomes

The effect of exogenous lysophosphatidylcholine on the membranes of liposomes containing protein has been studied. Lysophosphatidylcholine severely damaged liposomes prepared in the presence of membrane proteins such as glycophorin and "band 3" protein of human erythrocytes. Some basic proteins such as cytochrome c, lysozyme and polylysine also could sensitize liposomes to lysophosphatidylcholine. As described in previous papers (Inoue, K., et al. (1974) Biochim. Biophys. Acta 363, 361-372; Utsumi, H., et al. (1978) Biochemistry 17, 1990-1996), large multilamellar liposomes without protein were affected by lysophosphatidylcholine only under certain conditions where a phase boundary could exist. Sonicated liposomes without protein were almost completely insensitive to lysophosphatidylcholine. Liposomes prepared by the cholate dialysis method were also insensitive to lysophosphatidylcholine, irrespective of the incubation temperature. It is known that natural membranes such as membranes of erythrocytes and of other mammalian cells are rather sensitive to lysophosphatidylcholine. The difference observed between natural membrane and liposomal membrane seems to be removed by the introduction of proteins into lipid bilayers. The mode of interaction of lysophosphatidylcholine with membranes of liposomes containing protein is discussed.