We raised a monoclonal antibody, MA0, which reacts with A0, a 94-kDa rabbit skeletal muscle dystrophin-associated protein (DAP) bound to the syntrophin-binding domain of dystrophin. The antibody also reacted with the 62-kDa DAP which was moved to the locus close to beta-syntrophins by 2-dimensional PAGE, but the DAP did not coincide with any known beta-syntrophins. We have cloned a fragment of cDNA which codes the protein reacting with MA0 from a neonatal rabbit heart cDNA library. Based on the coincidence of cDNA sequences and the similarity in molecular mass, we concluded that the proteins reacting with MA0 are rabbit homologues of the Torpedo 87K protein.