Dystrophin, the protein product of the Duchenne/Becker muscular dystrophy gene has been localized in muscle to the inner surface of the plasma membrane and is likely to be associated with an integral membrane glycoprotein. The potential to make multiple isoforms via alternate splicing at the carboxyl domain of dystrophin suggests that it may interact with a variety of proteins in neuronal and muscle tissues and have a structural role similar to the cytoskeletal proteins alpha-actinin and spectrin.