LOSS OF ROTATIONAL MOBILITY OF BAND-3 PROTEINS IN HUMAN ERYTHROCYTE-MEMBRANES INDUCED BY ANTIBODIES TO GLYCOPHORIN-A

The effect of antibodies to glycophorin A on the rotational diffusion of band 3 in human erythrocyte membranes was investigated by transient dichroism. Three antibodies that recognize different epiptopes on the exofacial domain of glycophorin A all strongly reduce the rotational mobility of band 3. The effect is at most only weakly dependent on the distance of the epitope from the membrane surface. The degree of immo bilization obtained with two of the antibodies, BRlC14 and R18, is ver y similar to that produced by antibodies to band 3 itself. Similar res ults were obtained with membranes stripped of skeletal proteins. Fab f ragments and an antibody to glycophorin C had no effect on band 3 rota tional mobility. These results rule out a mechanism whereby band 3 rot ational immobilization results from enhanced interactions with the mem brane skeleton that are mediated by a conformational change in glycoph orin A. Rather, they strongly indicate that the antibodies to glycopho rin A cross-link existing band 3-glycophorin A complexes that have lif etimes that are long compared with the millisecond time scale of the t ransient dichroism measurements.