Studies on Human Serum High-Density Lipoproteins

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Abstract
Purified high-density lipoprotein (HDL), obtained by preparative ultracentri-fugation at density 1.063–1.19 g/ml in the cold, were subfractionated by hydroxyl apatite column chromatography. Two of the obtained subtractions (subtractions II and III) turned turbid after incubation at 37d` C for 12 h. The turbid material was recovered in the supernatant of D 1.006 g/ml after centrifugation at 30,000 g for 2 h. The lipoprotein fraction causing the turbidity was composed of 94% cholesterol ester and 2% apolipoprotein (by weight). On polyacrylamide gel electrophoresis the apolipoprotein moiety appeared as one polypeptide with the electrophoretic mobility of polypeptide A-I, revealed a blocked NH2-terminal amino acid, and had a total amino acid composition that differed from that of A-I and of the arginine-rich polypeptide.