Identification of the Blood‐Group ABH‐Active Glycoprotein Components of Human Erythrocyte Membrane

The blood‐group ABH‐active components of the erythrocyte membrane were identified by incubation of polyacrylamide gels after electrophoresis with radio‐iodinated blood‐group‐specific lectins. The anti‐A and anti‐B lectin of Bandeiraea simplicifolia bound to components from A 1 , AB and B erythrocytes but not A 2 or O erythrocytes, whereas the opposite was observed for the anti‐H lectin of Lotus tetragonolobus. Both lectins revealed as major blood‐group‐active components band 3 and the region of band 4.5, which was resolved into at least two components. Smaller amounts of the lectins were bound to the low‐molecular‐weight region and the dye front, which contained the poly(glycosyl)ceramides. In addition to these components, the B. simplicifolia lectin also bound to the sialoglycoprotein bands 1 and 2 (stained with periodic acid/Schiff). The distribution of bound radioactivity, as determined with this lectin was: Band 3, 22–25%; HIO 4 /Schiff band‐1, 10–15%; band 4.5, 34–37%; HIO 4 /Schiff band‐2, 12–15%; and the poly(glycosyl)ceramide region, 14–17%. The different lectin‐binding properties indicate a structural difference between the antigenic determinants of the sialoglycoproteins and of the other blood‐group‐active components. It is suggested that the antigenic determinants in the sialoglycoproteins are of the alkali‐labile type previously characterized, and that the carbohydrate chains of bands 3 and 4.5 correspond to the previously isolated alkali‐stable poly(glycosyl)peptides. The detection of two different groups of glycoproteins could thus explain the controversy concerning the nature of the blood‐group ABH antigens in glycoproteins of the erythrocyte membrane.