title: Interaction of the apoproteins of very low density and high density lipoproteins with synthetic phospholipids.
abstract: The interaction of synthetic dimyristoyl phosphatidylcholine (lecithin) liposomes with isolated apoC-I and apoC-III proteins from very low density lipoproteins has been studied by microcalorimetry. Complex formation is a highly exothermal process characterized by a maximal enthalpy of -130 kcal/mol (-544 kJ) apoC-III-1 and -65 kcal/mol apoC-I proteins (-272 kJ). The complex composition determined after its isolation by ultracentrifugal flotation agrees with the value derived from the enthalpy binding curves. The binding of a constant amount of dimyristoyl lecithin to apoprotein mixtures containing various proportions of apoA-I and apoC-III failed to demonstrate the existence of any preferential association between the two apoproteins, in contrast with results obtained previously with apoA-I/apoA-II protein mixtures. Finally the various contributions to the enthalpy of binding such as that arising from an increase in apoprotein helicity have been evaluated. A classification of the apolipoproteins according to their lipid-binding affinity is proposed as: apoA-II congruent to apoC-III greater than apoC-I greater than apoA-I proteins.
mesh_terms: D001053:Apolipoproteins / Q000097:blood; D001665:Binding Sites; D002151:Calorimetry; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008081:Liposomes; D009227:Myristic Acids; D010713:Phosphatidylcholines; D011485:Protein Binding; D013816:Thermodynamics
chemical_list: D001053:Apolipoproteins; D008075:Lipoproteins, HDL; D008079:Lipoproteins, VLDL; D008081:Liposomes; D009227:Myristic Acids; D010713:Phosphatidylcholines