THE SEQUENCE, BACTERIAL EXPRESSION, AND FUNCTIONAL RECONSTITUTION OF THE RAT MITOCHONDRIAL DICARBOXYLATE TRANSPORTER CLONED VIA DISTANT HOMOLOGS IN YEAST AND CAENORHABDITIS-ELEGANS

The dicarboxylate carrier (DIC) belongs to a family of transport prote ins found in the inner mitochondrial membranes. The. biochemical prope rties of the mammalian protein have been characterized, but the protei n is not abundant. It is difficult to purify and had not been sequence d. We have used the sequence of the distantly related yeast DIC to ide ntify a related protein encoded in the genome of Caenorhabditis elegan s, Then, related murine expressed sequence tags were identified with t he worm sequence, and the murine sequence was used to isolate the cDNA for the rat homolog, The sequences of the worm and rat proteins have features characteristic of the family of mitochondrial transport prote ins. Both proteins were expressed in bacteria and reconstituted into p hospholipid vesicles where their transport characteristics closely res embled those of whole rat mitochondria and of the rat DIC reconstitute d into vesicles. As expected from the role of the DIC in gluconeogenes is and ureogenesis, its transcripts were detected in rat liver and kid ney, but unexpectedly, they were also detected in rat heart and brain tissues where the protein may fulfill other roles, possibly in supplyi ng substrates to the Krebs cycle.