Polypeptides from serum low-density lipoproteins of pigs (Sus domesticus)

Low-density lipoproteins floating between densities 1-006 and 1-063 g cm-3 were isolated by centrifugation of blood serum obtained from 24-h fasted pigs (Sus domesticus). This lipoprotein fraction contained two components with Sf 1-063 values of 3-4 and 2-3 at 20 degrees C when examined by analytical ultracentrifugation. Delipidation of the lipoprotein yielded 15% recovery of soluble protein. Chromatography on Sephadex G100 in 8 M urea of these delipidation products yielded three fractions of different sizes which were present in both native and succinylated apoproteins. These fractions from the succinylated apolipoproteins were further characterized. A polypeptide fraction comprising 70% of the total protein had an apparent molecular weight of 34000 and contained greater amounts of amino acids with hydrophobic side chains than did the second fraction of apparent molecular weight 22000 which contained 15% of the protein. The third fraction of apparent molecular weight 12500 contained 15% of the protein.