Properties of liposomes with a phospholipid ratio similar to that of retinal rod outer segment membranes: Interaction with opsin and other proteins

Liposomes have been prepared with a phospholipid ratio and a cholesterol content similar to that of the outer segments of rod photoreceptor cells. Studies were made of the appearance, electrophoretic mobility and sodium leakage rates of the liposomes, with and without the inclusion of protein (albumin, myoglobin, ribonuclease, lysozyme, proteolipid or opsin). The findings indicate that although the appearance and properties of these liposomes closely resemble those of other liposomes reported in the literature, the liposomes become markedly changed in appearance, electrophoretic mobility and sodium permeability by the addition of opsin. These data emphasize the hydrophobic nature of the opsin-lipid interaction and suggest an ability of opsin to alter the ion leakage properties of a rod outer segment membrane.