Further Characterization of Apolipoproteins from the Human Plasma Very Low Density Lipoproteins

Abstract

Abstract Valine apolipoprotein, glutamic acid apolipoprotein, and alanine apolipoprotein (apoLP-Ala) (designated by their COOH-terminal amino acids) are three small apolipoproteins which constitute more than half of the protein in human plasma very low density lipoprotein. These proteins were isolated free of lipid by techniques previously described. As determined by sedimentation equilibrium analysis and estimated from amino acid analyses, the approximate molecular weights of the apolipoproteins were: valine apolipoprotein, 7,000; glutamic acid apolipoprotein, 10,000; and apoLP-Ala, 10,000. Circular dichroism and optical rotatory dispersion spectra for valine apolipoprotein were consistent with a high content of α helix, while the spectra obtained with apoLP-Ala suggested its structure to be mainly of random coil. Previously reported polymorphism of apoLP-Ala was found to be attributed to differences in content of sialic acid.