Isolation and Characterization of a Glycoprotein from Human Group O Erythrocyte Membrane

Abstract

Abstract A glycoprotein was isolated from human group O erythrocyte membranes previously treated with detergents by a mild extraction with 90% phenol and further purified by successive passages through columns of DEAE-, CM-Sephadex, and Sephadex G-100 followed by a chloroform-methanol extraction. The purified glycoprotein appeared to be a single molecular species in gel filtration, polyacrylamide electrophoresis, and ultracentrifugation, and a molecular weight of 53,000 was estimated by sedimentation equilibrium experiments in the presence of 1% sodium dodecyl sulfate. This glycoprotein, which contains 55% carbohydrate, has H and MN blood group activities and carries the receptors for various phytohemagglutinins. After alkaline, reductive degradation of the glycoprotein, the blood group H and MN activities were greatly diminished, whereas the inhibitory activities against certain phytohemagglutinins, especially concanavalin A, were remarkably enhanced, indicating that the antigenic receptors of the former blood group activities clearly reside in alkali-labile O-glycosidically linked oligosaccharide chains and the receptors for the latter phytohemagglutinins mostly reside in alkali-stable N-glycosidically linked oligosaccharide chains. The purified glycoprotein was also found to be a potent inhibitor for [3H]thymidine incorporation in human lymphocytes stimulated by various phytomitogens and anti-lymphocyte serum.