Fusion of Large Unilamellar Liposomes Containing Hemocyanin with Planar Bilayer Membranes

Membrane Fusion, Large Liposomes, Planar Bilayer, Hemocyanin Channel, Asymmetrical Insertion Large unilamellar vesicles were prepared by detergent removal from micelles containing phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Liposomes were then interacted with Megathura crenulata hemocyanin, a well studied channel former. Incubation of the resulting proteoliposomes on one side of a phosphatidylserine-containing planar bilayer under fusion conditions yielded strong current increases. Such increase is due to insertion of ionic channels from the liposomes into the planar bilayer. Studying the effects of Ba2+ on the electrical properties of the channel we could show that the protein is always inserted into a bilayer during this process, i.e. fusion of proteoliposomes with the artificial m em brane occurs. The strong non linearity of the current-voltage curve of the hemocyanin pore could be used as a probe of the extent to which fusion preserves the orientation of the channel through the bilayer.