A POLYPEPTIDE DERIVED FROM MITOCHONDRIAL DIHYDROLIPOAMIDE SUCCINYLTRANSFERASE IS LOCATED ON THE PLASMA-MEMBRANE IN SKELETAL-MUSCLE

Dihydrolipoamide succinyltransferase (DLST) is the core-enzyme of 2-ox oglutarate 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 antibod y besides mitochondria. Furthermore, subcellular fractionation analysi s coupled with Western blotting demonstrated that the antigen of the a nti-DLST antibody is distributed on the plasma membrane fraction in ad dition to the mitochondria fraction in skeletal muscle and that it is free from the complex. The molecular weight of the polypepetide bound to the plasma membrane was about 20 kilodaltons (kDa). The polypeptide was purified by immunoprecipitation and its N-terminal amino-acid seq uence was determined. The aminoacid sequence exactly corresponded to a part of DLST. Northern blots revealed the presence of mRNA correspond ing to the 20 kDa protein. We are the first to report that a mitochond rial protein is also present on the plasma membrane in skeletal muscle as well as in mitochondria. (C) 1997 Academic Press.