Reconstitution of lipoproteins. II. Lipid-protein interaction between dimyristoyl-lecithin and dimyristoyl-lecithin:cholesterol vesicles and purified apolipoprotein C-I and C-III2 studied by isomeric spin-labelled lecithins.
The reconstitution of purified apolipoprotein C-I and C-III2 with sn-3-dimyristoyl-lecithin and sn-3-dimyristoyl-lecithin:cholesterol (10:1) vesicles was studied by electron spin resonance spectroscopy using isomeric 5'-, 12'-, and 16'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithin probes. Results obtained from the temperature-induced changes of lipoprotein recombinants showed the hydrophilic nature of the lipid-protein interactions. The temperature-induced phospholipid phase transition, as measured by 5'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithin probe in recombinants containing apoprotein C-1 or apoprotein C-iii2, is very broad and has a small cooperative unit indicative of extensive lipid-protein interactions occurring at the head group region of the phospholipid bilayer. When 12"- and 16'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithins are used as probes in the same system, similar sharper and more cooperative lipid phase changes are detected. These results indicate a surface location for both apoprotein C-I and apoprotein C-III2 with respect to the phospholipid bilayer in lipoprotein recombinants with and without cholesterol.
D000596:Amino Acids / Q000032:analysis; D053302:Apolipoprotein C-I; D053305:Apolipoprotein C-III; D001053:Apolipoproteins; D001056:Apolipoproteins C; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D007525:Isoelectric Focusing; D008081:Liposomes; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D010713:Phosphatidylcholines; D013113:Spin Labels
D000596:Amino Acids; D053302:Apolipoprotein C-I; D053305:Apolipoprotein C-III; D001053:Apolipoproteins; D001056:Apolipoproteins C; D008081:Liposomes; D046911:Macromolecular Substances; D010713:Phosphatidylcholines; D013113:Spin Labels; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine