Partial Purification of Apolipoprotein E Receptor of Rat Liver Membrane

Abstract

Liver has two distinct lipoprotein receptors; one is apolipoprotein (apo) B, E receptor and the other is apo-E receptor. We partially purified apo-E receptor protein from solubilized rat liver membranes using ion exchange chromatography and preparative gel electrophoresis.
Rat liver membrane was prepared by ultracentrifugation as the 8, 000 to 100, 000×g pellets after the homogenation. The liver membrane was solubilized in the presence of 40mM octylglucoside. Ligand blotting of the solubilized liver membrane protein, using HDLc as a ligand, revealed that two bands were visualized besides that of the apo-B, E receptor. Molecular weights of these proteins were estimated to be about 60K and 36K on 14% SDS-PAGE. The 36K protein was separated from the apo-B, E receptor protein using preparative gel electrophoresis. The binding of ¹²⁵I-HDLc to the isolated 36K protein showed a saturable manner, and was inhibited only by HDLc competitively but not by human LDL and canine HDL. These findings suggest that the 36K protein is the apo-E receptor.