The incorporation of partially delipidized proteolipid proteins from Torpedo marmorata electroplax into liposomes

The preparation of proteoliposomes from pure phospholipids and partially delipidized proteolipid proteins from Torpedo marmorata electroplax is described. The resulting vesicles are morphologically different from their lipid counterparts, the main feature being a reduction in the number of lamellae. These structures are highly permeable toward Rb⁺, K⁺, or glucose. The association between the proteolipid proteins and the phospholipids is not modified by increasing the amount of acidic phospholipids or cholesterol in the liposomes. The partially delipidized proteolipid proteins are capable of reducing the phasetransition temperature of dipalmitoylphosphatidylcholine. It is suggested that during the liposome formation procedure there is an interaction between the proteolipid proteins and the lipids, probably via hydrophobic associations. This gives rise to highly permeable, more fluid structures compared to pure phospholipid vesicles.