Proteolytic degradation of human erythrocyte band 3 by membrane-associated protease activity

Antisera directed against the cytoplasmic portion of human erythrocyte Band 3 were used to follow the degradation of the band 3 molecule. Small amounts of Band 3 were degraded when well-washed red cell membrane ghosts were incubated in the cold; this process was greatly accelerated by incubating ghosts were incubated in the cold; this process was greatly accelerated by incubating ghosts at 37 degrees C. Band 3 labeled with pyridoxal-phosphate was digested at comparable rates. Band 3 digestion also took place when alkali-extracted ghost membranes were incubated at 37 degrees for prolonged periods. These results suggest that human erythrocytes contain tightly bound, membrane-associated proteolytic activity.