Distribution of glycophorin on the surface of human erythrocyte membranes and its association with intramembrane particles: an immunochemical and freeze-fracture study of normal and En(a-) erythrocytes.

Abstract

Human erythrocyte membranes of the En(a-) blood group lack the major sialoglycoprotein (glycophorin). By absorption of a crude antiglycophorin antiserum with En(a-) membranes a specific antiglycophorin antiserum was obtained. By immune electron microscopy we showed that glycophorin is randomly distributed on the surface of normal erythrocytes. When polycationized ferritin, which mainly binds to glycophorin, was used as a marker a similar even labeling of normal erythrocyte membranes was seen. En(a-) membranes bound much less of this marker. In freeze-fracturing the intramembrane particles of both membrane types had a similar distribution and appeared in equal amounts. However, partial removal of spectrin from these membranes, followed by incubation at pH 6 resulted in more extensive aggregation of the particles in En(a-) membranes than in normal membranes. The results may be interpreted as glycophorin contributing by electrostatic repulsion to the random distribution of the intramembrane particles in normal cells. This repulsion is weakened in in En(a-) cells by the lack of glycophorin.