Protein content and composition of human high density lipoprotein subfractions.

High density lipoprotein (HDL) was fractionated by ion exchange column chromatography using a continuous NaCl gradient of 0.06--0.13 M. It was found that, on the basic C apoprotein content, HDL is comprised of 3 subfractions. All 3 subfractions contain apo A-I and apo A-II but the apo A-I/apo A-II ratio is different in each subfraction and in the case of subfraction c, that fraction which eluted at highest NaCl concentrations, the A-I/A-II ratio varied even within this subfraction. Subfraction a contained no C apoprotein, subfraction b contained apo C-II and apo C-III-1 but no apo C-III-2 while subfraction c contained apo C-III-2 and trace amounts of apo C-II and C-III-1. Analysis of HDL2 and HDL3 shows that both contain all 3 lipoprotein subfractions, but in differing quantities.