Dystrophin is purified as a complex with several proteins from the digitonin-solubilized muscle cell membrane. Most of dystrophin-associated proteins (DAPs) are assumed to form a large oligomeric transmembranous glycoprotein complex on the sarcolemma and link dystrophin with a basement membrane protein, laminin. In the present study, we found that the purified dystrophin-DAP complex was dissociated into several groups by n-octyl-beta-D-glucoside treatment. In particular, we found that the glycoprotein complex stated above was dissociated into two distinct groups: one composed of 156DAG and 43DAG (A3a) and the other composed of 50DAG, 35DAG and A3b. We confirmed by crosslinking and immunoaffinity chromatography that these two groups existed in a complexes. We thus concluded that the glycoprotein complex consists of these two subcomplexes. Furthermore, A3b and 43DAG, which had been formerly treated simply as the 43DAG doublets due to their similar electrophoretic mobilities in SDS/PAGE, were shown to be present in two different subcomplexes. Based on the analyses by two-dimensional gel electrophoresis, peptide mapping and immunoblotting, we concluded that A3b is a novel DAP different from 43DAG.