Heterogeneity of molecular weight and apolipoproteins in low density lipoproteins of healthy human males.

The molecular weights of five low density lipoprotein (LDL) subfractions from four normal healthy males were determined by analytic ultracentrifuge sedimentation equilibria. Protein content of each subfraction was determined by elemental CHN analysis, and weights of apoprotein peptides were calculated. Molecular weights in subfractions of increasing density were 2.92 +/- 0.26, 2.94 +/- 0.12, 2.68 +/- 0.09, 2.68 +/- 0.28 and 2.23 +/- 0.22 million Da, and protein weight percentages were 21.05, 21.04, 22.05, 23.10 and 29.10, in subfractions 1, 2, 3, 4 and 5, respectively. Total mean apoprotein weights for respective subfractions were 614 +/- 53, 621 +/- 45, 588 +/- 9, 637 +/- 83 and 645 +/- 62 KDa. In addition to a single apoprotein B-100 (apo B-100) peptide with a mean carbohydrate content of 7.1% and a molecular weight of 550 KDa per LDL particle, there may be one or more apoprotein E peptides of 34 KDa and/or apoprotein C-III of 9 KDa. In addition, subfractions 4 and 5 may contain 3-7% apolipoprotein (a). There is considerable heterogeneity among LDL subfractions as well as within the same fraction from different individuals. This heterogeneity may relate to differences in origin, metabolism and/or atherogenicity as a result of their content of apoproteins other than apo B-100.