Effect of sulfhydryl reagents on spectrin states on the erythrocyte membrane.

The unique properties of erythrocytes are largely determined by its fibrillar network under the plasma membrane. Spectrin, one major component of the membrane skeleton, has been suggested to play a central role in this process. To understand the mechanism underlying this process, the effect of the sulfhydryl groups of erythrocyte membrane on spectrin structure and function was studied. By using non-denaturing gel analysis, dithiothreitol was found to protect spectrin in its tetramer state. In contrast, iodoacetamide and N-ethylmaleimide enhanced conversion of the spectrin tetramer to dimer and decreased its binding to the membrane. Moreover, when the membrane was treated with cadmium, the tetramer was converted to the dimer on the membrane, while zinc had no effect. Hemolysis experiments showed that cadmium could lyse erythrocytes in vitro. These results indicated that preservation of the spectrin tetramer or even higher oligomer states, by the sulfhydryl groups may be important to the membrane integrity and the intact cell functions.