Soybean Protein Products as Regulators of Liver Low-Density Lipoprotein Receptors. I. Identification of Active β-Conglycinin Subunits

Abstract

The ability of the different soy globulins to upregulate low-density lipoprotein (LDL) uptake and metabolism in human hepatoma cells (Hep G2) was investigated, in an attempt to identify peptide components responsible for the upregulation of the LDL receptor. In parallel, the metabolism of soy globulins, added to the culture medium, was investigated by two-dimensional electrophoresis. After addition of soy globulins, there were no marked changes in the cell protein pattern, as evaluated by general protein staining. By immunodetection, intact 7S components were observed both free in the culture medium and bound to plasma membranes. Inside cells, α + α‘ subunits in their native forms were not detectable, whereas most of the β chain was found unchanged. Largely unmodified soybean proteins were detected in a lysate of 11S-treated cells. Incubation of Hep G2 cell with purified α + α‘ from 7S sharply increased uptake and degradation of 125I-LDL added to the culture medium, whereas the β chains were ineffective; ...