Identification of the lipid-binding cyanogen bromide fragment from the cystine-containing high density apolipoprotein, ApoLP-Gln-II

ApoLP-Gln-II is one of the major protein constituents of human plasma high density lipoproteins (HDL). This protein and its two CNBr fragments, C-III (carboxyl-terminal) and C-IV (amino-terminal) were tested for ability to bind phosphatidyl choline by the formation of lipid-protein complexes of density 1.063 to 1.210 gm/ml, by changes induced in circular dichroism, and by the inhibition of the reactivation of delipidated mitochondrial β-hydroxybutyric dehydrogenase. In all three of these experimental procedures, C-III but not C-IV retained the ability to bind phosphatidyl choline. These findings suggest that the phospholipid binding site(s) of apoLP-Gln-II may be localized in the carboxyl-terminal portion of the molecule.