The muscular dystrophies--from genes to proteins.

proteins, which link the activity contracting action and myosin components to the non-contracting structures in the fiber and outside, are defective. In our article we will strictly confine ourselves to this anchoring device which is called the dystrophin glycoprotein complex (DGC). As shown in Fig. 1 (after Lim and Campbell) dystrophin, the gene product defective in DMD, is a large rod-shaped cytoskeletal protein, which is entirely intracellular, is bound the F-action contractile protein on its one end, while its other end, near the plasma membrane, is attached to at least three groups of protein molecules which have a complex interrelation amongst themselves. The dystroglycan complex is one of these proteins and is composed of two large subunits the α and the β dystroglycans respectively. The α destroglycan is entirely extracellular and is attached at one end to laminin which is the actual extracellular anchor protein. The other end of α dystroglycan attaches itself to the β-submit which is the trans-membrane protein binding to the cystein-rich region of dystrophin on the intracellular part and the α-subunit on the extracellular part.