Dystrophin–glycoprotein Complex Purified from Hamster Cardiac Muscle. Comparison of the Complexes from Cardiac and Skeletal Muscles of Hamster and Rabbit

The dystrophin–glycoprotein complex was isolated from hamster ventricular muscle by a method involving homogenization of muscle directly in the presence of 1% digitonin, followed by chromatography on succinylated wheat germ agglutinin agarose, Diethyl aminoethyl (DEAE) cellulose, and/or immunoaffinity agarose. Protein yield of the DEAE cellulose-purified dystrophin–glycoprotein complex was 120±30 (n=3)μg per 5 g hamster ventricular muscle. The cardiac dystrophin–glycoprotein complex, unlike the skeletal muscle counterpart, could not be solubilized from a microsomal fraction with digitonin or some other detergents. By sodium dodecyl sulfate gel electrophoresis, protein composition of the dystrophin–glycoprotein complexes from hamster cardiac muscle was found to be significantly different from that of rabbit skeletal muscle which has been extensively studied. This difference mainly arises from the species difference, because in hamster the cardiac and skeletal muscle complexes exhibited essentially the same protein composition. In rabbit, on the other hand, there are differences between the cardiac and skeletal complexes in the relative abundance of 60 and 64 kDa proteins and in the apparent M_rofα-dystroglycan. We found that the content of the dystrophin–glycoprotein complex, estimated by quantitative immunoblot assay, is at least 5 times more abundant in cardiac than in skeletal muscle in hamster and rabbit.