Isolation and characterization of a human serum cholesteryl ester transfer protein

Human plasma has been shown to contain an apolipoprotein that mediates the transport of cholesteryl ester from high density lipoprotein (HDL) to very low density lipoprotein (VLDL) or low density lipoprotein (LDL). This activity, confined to the density greater than 1.063 g/ml interval, has been isolated from HDL and appears as a single migrating species by anionic or sodium dodecyl sulfate/polyacrylamide gel electrophoresis. It is unreactive to antibodies to the major HDL apolipoproteins. Antibodies prepared against this factor and immobilized on Sepharose remove the capacity of HDL and density greater than 1.21 g/ml fractions as well as whole plasma to transport cholesteryl ester from HDL. The system shows saturation kinetics with respect to plasma LDL and VLDL concentrations, and transport of cholesteryl ester was associated with reciprocal and equimolar back-transport of triglyceride from VLDL and LDL to the HDL fraction. The possible relationship of this apoprotein to apoprotein D is discussed.