Glycophorin and the concanavalin A receptor of human erythrocytes: their receptor function in lipid bilayers.

Abstract

Integral glycoproteins (2) from the human erythrocyte were studied after their incorporation into lipid bilayer systems. Glycophorin (M/N blood group determinant) and the concanavalin A receptor were isolated and purified prior to incorporation into model membranes by dialytic removal of detergent from lipid/protein solutions. Under the conditions described, glycoprotein receptors maintain their function in that they bind external agents specific for them, such as concanavalin A and immunoglobulins. So-called intramembranous particles are a feature of freeze-fractured preparations of lipid bilayers containing either (or both) glycoprotein(s), and to some extent each has a characteristic particle appearance. Liposomes containing the concanavalin A receptor (with or without glycophorin) are agglutinable by concanavalin A, whereas human erythrocytes are normally considered to be nonagglutinable by this lectin. Liposomes containing glycophorin alone are readily agglutinable by the appropriate glycophrorin-directed M/N antiserum, as are human erythrocytes. The added presence of concanavalain A receptor in the liposomes can markedly inhibit agglutination by M/N antiserum without preventing immunoglobulin binding.