Micellar complexes of human apolipoprotein A-I with phosphatidylcholines and cholesterol prepared from cholate-lipid dispersions.

摘要: Micellar complexes of human apolipoprotein A-I and phosphatidylcholine, with or without cholesterol, were prepared by adding (apo A-I) to sodium cholate-lipid mixtures. Cholate was removed dialysis the apo A-I.lipid isolated gel filtration chromatography density gradient ultracentrifugation. The lipid mixtures consisted dipalmitoylphosphatidylcholine egg yolk phosphatidylcholine in presence various molar ratios cholesterol. formation examined at different (PC)-to-apo ratios, PC-to-cholate cholate concentrations. Yields maximal when incubation performed near transition temperature PC. Upon binding complex formation, experienced a significant increase alpha-helix content, blue shift intrinsic tryptophan fluorescence. In all lipid-protein mixtures, from 600:1 75:1, PC/apo (molar ratios), relatively small, stable present which gave maximum yields similar their stoichiometries 75:1 140:1, ratios). For complexes, molecular weights determined sedimentation equilibrium be range 220,000 260,000; fluorescence polarization using hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene showed broadened shifted liquid-crystalline phase transition, characteristic micellar Complexes A-I, covalently labeled 5-dimethylaminonaphthalene-1-sulfonyl chloride, had an overall particle rotational relaxation time 530 ns. On electron micrographs, negatively stained phosphotungstate, appeared as lamellar, discoidal particles.