Membrane skeleton and diminution of transmembrane proteins and calmodulin in erythrocytic vesicles

During preservation of erythrocytes vesicles are formed, the membranes of which do not contain membrane skeleton components (spectrin, actin). In comparison to the normal erythrocyte membrane (100%) the vesicle membrane exhibits significantly lowered amounts in band 3 protein (14-17%), sialic acid (30-40%), (Ca2+ + Mg2+)ATPase (6%) and (Na+ + K+)ATPase (28%). The losses in band 3 protein, glycophorin A (calculated from the decrease of sialic acid) and in the number of the intramembranous particles correspond to one another. The calmodulin concentration of the vesicles was estimated to be 35% that of the erythrocytes in maximum. The findings indicate a binding of these components to the membrane skeleton. The nature of the binding of the transmembrane proteins as well as the consequences of these results regarding the composition of the intramembranous particles are discussed.