Lipid transport and lipoprotein interconversions

¹ Departments of Biochemistry and Medicine, Baylor University College of Medicine, Houston, Texas

Serum lipoproteins were isolated from various sources including normal and hyperlipemic human, dog, and rabbit serum through preparative ultracentrifugation. These lipoprotein fractions were extracted with cold ether, and the ether-modified products were studied for sedimentation and flotation properties in an analytical ultracentrifuge. Results indicate that a relatively small number of ether-modified residues are obtained from the entire lipoprotein spectrum of all species studied. It is suggested that these moieties may be closely related to actual lipid-transporting components of the lipoprotein system. In addition, a fraction of lipoprotein-free human serum (probably closely related to beta globulin) has been identified, which will bind certain phospholipids. This protein-phospholipid complex may be separated from other serum proteins through ultracentrifugation and studied electrophoretically.