Two-dimensional electrophoretic analysis of human erythrocyte cylindrin.

Cylindrin, a macromolecule isolated from the human erythrocyte, and the band 7 proteins of the erythrocyte membrane were analyzed by one- and two-dimensional electrophoresis. Cylindrin was recovered from both the cytosol and cell membranes of hypotonically lysed erythrocytes, and its identity was confirmed by electrophoresis and transmission electron microscopy. Cylindrin from either source produced eight bands on one-dimensional SDS gels, and seventeen spots on two-dimensional gels, revealing a more complex composition than previously reported. It is unlikely that this complexity was due to proteolysis, since preparations of cylindrin with various protease inhibitors gave the same electrophoretic patterns. Mixing experiments showed that the polypeptide subunits of the cylindrin complex are distinct from the band 7 proteins of the erythrocyte membrane. This finding failed to support a role for the cylindrin macromolecule in the permeability disorders of the erythrocyte membrane associated with a missing band 7 protein.