title: Barrier properties of glycophorin-phospholipid systems prepared by different methods.
abstract: Glycophorin was incorporated into large unilamellar dioleoylphosphatidylcholine vesicles by either a detergent dialysis method using octylglucoside or a method avoiding the use of detergents. The vesicles were characterized and the permeability properties and transbilayer movement of lipids in both vesicles were investigated as a function of the protein concentration and were compared to protein-free vesicles. An insight in the permeability properties of the vesicles was obtained by monitoring the ratio potassium (permeant): dextran (impermeant) trap immediately after separation of the vesicles from the external medium. Glycophorin incorporated without the use of detergents in 1:300 protein:lipid molar ratio induces a high potassium permeability for the majority of the vesicles as judged from the low potassium trap (K+:dextran trap = 0.21). In contrast, the vesicles in which glycophorin is incorporated via the octylglucoside method (1:500 protein:lipid molar ratio) are much less permeable to potassium (K+:dextran trap = 0.67 and t12 of potassium efflux at 22 degrees C is 7.5 h.). The relationship between protein-induced bilayer permeability and lipid transbilayer movement in both vesicle preparations is discussed. Addition of wheat-germ agglutinin to glycophorin-containing vesicles comprised of dioleoylphosphatidylcholine and total erythrocyte lipids caused no or just a small effect (less than 20% release of potassium) on the potassium permeability of these vesicles. Also, addition of lectin to dioleoylphosphatidylethanolamine-glycophorin bilayer vesicles in a 25:1 lipid:glycophorin molar ratio had no effect on the permeability characteristics of the vesicles. In contrast, addition of wheat-germ agglutinin to bilayer vesicles made of dioleoylphosphatidylethanolamine and glycophorin in a 200:1 molar ratio resulted in a release of 74% of the enclosed potassium by triggering a bilayer to hexagonal (HII) phase transition. The role of protein aggregation and the formation of defects in the lipid bilayer on membrane permeability and lipid transbilayer movement is discussed.
mesh_terms: D004910:Erythrocyte Membrane / Q000378:metabolism; D006021:Glycophorins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D037102:Lectins; D008051:Lipid Bilayers; D008244:Lysophosphatidylcholines; D009682:Magnetic Resonance Spectroscopy; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011188:Potassium / Q000378:metabolism; D011663:Pulmonary Surfactants; D012795:Sialoglycoproteins / Q000378:metabolism*; D014909:Wheat Germ Agglutinins
chemical_list: D006021:Glycophorins; D037102:Lectins; D008051:Lipid Bilayers; D008244:Lysophosphatidylcholines; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011663:Pulmonary Surfactants; D012795:Sialoglycoproteins; D014909:Wheat Germ Agglutinins; C020888:1,2-dielaidoylphosphatidylethanolamine; C017251:1,2-oleoylphosphatidylcholine; D011188:Potassium