IN-VITRO EXPRESSED DYSTROPHIN FRAGMENTS DO NOT ASSOCIATE WITH EACH OTHER

Dystrophin, a component of the muscle membrane cytoskeleton, is the pr otein altered in Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD), Dystrophin shares significant homology with other cy toskeletal proteins, such as alpha-actinin and spectrin, On the basis of its sequence similarity with alpha-actinin and spectrin, dystrophin has been proposed to function as dimer, However, the existence of bot h dimers and monomers have been observed by electron microscopy, To ad dress this apparent discrepancy, we expressed dystrophin fragments com posed of different domains in an in vitro translation system, The expr essed fragments were tested for their ability to interact with each ot her and full-length dystrophin by both immunoprecipitation and blot ov erlay assays. These assays were successfully used to demonstrate the d imerization of alpha-actinin and spectrin, yet failed to detect any in teraction between dystrophin fragments, Although these in vitro result s do not prove that dystrophin is not a dimer in vivo, they do indicat e that this interaction is not like that of the alpha-actinin and spec trin. (C) 1997 Federation of European Biochemical Societies.