Identification of dystrophin-binding protein(s) in membranes from Torpedo electrocyte and rat muscle.

Using solubilized dystrophin isolated from torpedo electric tissue and in vitro blot overlay assay, we have identified dystrophin-binding proteins in membranes from Torpedo electrocyte and rat muscle. In acetylcholine receptor-rich membranes from Torpedo marmorata electric tissue, an extrinsic protein of M(r) 52,000, known as the 58-kDa protein (Froehner, S.C. (1984) J. Cell Biol. 99, 88-96), represents the major binding site for dystrophin. When membranes were solubilized by non-ionic detergents, the 52-kDa protein as well as a few proteins of M(r) 200,000, 87,000, and 45,000 co-extract and copurify with dystrophin. In rat sarcolemma, a protein doublet of approximately 58-60 kDa also binds dystrophin in vitro, this protein likely being the DAP 59 characterized by Ervasti and Campbell (Ervasti, J. M., and Campbell, K. P. (1991) Cell 66, 1121-1131). We postulate that the 52- and 59-kDa proteins are functional homologs that play the role of "receptors" for dystrophin in various specialized membrane domains.