Further characterization of the erythrocyte membrane protein abnormality in megaloblastic anemia

Erythrocyte membranes obtained from patients with severe megaloblastic anemia contain spectrin as indicated by double immunodiffusion against anti-spectrin raised in rabbits. These membranes have normal protein patterns determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate after solubilization at 100 degrees C for 3 min in SDS. When incubation is carried out at 37 degrees C for 3 hours, however, the membrane protein patterns become grossly abnormal, lacking spectrin, band 3 and having several diffuse smaller bands. Cross-linking of these membranes with SH oxidizing agents, such as diamide prevented this dissociation phenomenon. The SH group content of megaloblastic membranes, both from severe and mild megaloblastic anemia, was significantly higher than that of control membranes. This was also confirmed by the greater incorporation of 3H-N-ethylmalemide into red cell membranes from mild and severe megaloblastic anemia than controls. Incorporation of this probe was greatest into the band 3 region. These findings indicate that the erythrocyte membrane proteins in megaloblastic anemia have an intrinsic abnormality which renders them more susceptible to degradation by their endogenous proteases.