Characterization of apolipoprotein E-rich high density lipoproteins in familial lecithin:cholesterol acyltransferase deficiency

We have isolated and charachterized a subfraction of high density lipoproteins, rich in apolipoprotein E, from the plasma of patients afflicted with familial lecithin:cholesterol acyltransferase deficiency. Prepared by successive ultracentrifugal flotation, affinity chromatography on heparin-agarose, and affinity chromatography on conconavalin A-agarose, the subfraction contained disc-shaped lipoproteins that measured 14–40 nm in diameter and 4.4–4.5 nm in thickness. The major components were apolipoprotein E, phosphatidylcholine, and unesterified cholesterol, though other apolipoproteins and lipids were present in small amounts. A second subfraction of high density lipoproteins, isolated during the chromatography, contained apolipoproteins A-I and A-II, but no apolipoprotein E. This subfraction included disc-shaped lipoproteins, 13–24 nm in diameter, as well as small round particles, 5.7 nm in diameter. Both subfractions contained similar proportions of total protein relative to lipid, similar amounts of unesterified cholesterol relative to phosphatidylcholine, and a similar distribution of phosphatidylcholine fatty acid.