Presence of spectrin tetramer on the erythrocyte membrane

In order to examine the subunit structure of membrane-associated spectrin, human erythrocyte membranes were cross-linked with a variety of photosensitive heterobifunctional reagents by flash photolysis millisecond cross-linking (Kiehm, D.J., and Ji, T.H. (1977) J. Biol. Chem. 252, 8524-8531). Cross-linking of ghosts produced a series of new bands with apparent molecular weights of approximately 420,000, 710,000, and 910,000, as well as a band at the top of the gels. Evidence is presented that these three bands represent spectrin dimer, trimer, and tetramer, respectively. We propose that spectrin tetramer exists on the membrane as the predominant structural unit and that dimer is not a repeating structural unit.