Dihydrolipoamide succinyltransferase (DLST) is the core-enzyme of 2-oxoglutarate dehydrogenase complex which is located in mitochondria. In this study, several tissues from rat and human were immunostained with an affinity-purified anti-DLST antibody. Of the tissues examined, the plasma membrane of skeletal muscle was immunostained with the antibody besides mitochondria. Furthermore, subcellular fractionation analysis coupled with Western blotting demonstrated that the antigen of the anti-DLST antibody is distributed on the plasma membrane fraction in addition to the mitochondria fraction in skeletal muscle and that it is free from the complex. The molecular weight of the polypeptide bound to the plasma membrane was about 20 kilodaltons (kDa). The polypeptide was purified by immunoprecipitation and its N-terminal amino-acid sequence was determined. The amino-acid sequence exactly corresponded to a part of DLST. Northern blots revealed the presence of mRNA corresponding to the 20 kDa protein. We are the first to report that a mitochondrial protein is also present on the plasma membrane in skeletal muscle as well as in mitochondria.