Isolation of a helical, lipid-binding fragment from the human plasma high density lipoprotein, apolp-GLN-I

The major apolipoprotein of human plasma high density lipoproteins (HDL), apoLP-Gln-I, has previously been shown to have a high content of α-helical conformation and a molecular weight of approximately 28,000. Our results show that apoLP-Gln-I contains three methionine residues. We have treated apoLP-Gln-I with cyanogen bromide (CNBr) and have isolated the four CNBr fragments by chromatography on BioGel P-30. One of the fragments, CNBr-I has 92 amino acid residues, contains no homoserine or methionine and corresponds to the carboxyl-terminal peptide. This fragment is of particular interest since it was shown to retain a high content of α-helix, while the other fragments were mainly disordered, and to possess the ability to bind phosphatidyl choline.