Functional Expression of the Tandem-Repeated Homodimer of the Mitochondrial ADP/ATP Carrier in Saccharomyces cerevisiae

The mitochondrial ADP/ATP carrier (AAC) is believed to function as a dimer. To characterize the oligomeric state of the yeast type 2 AAC (yAAC2), we tried to express its tandem-repeated homodimer, in which the C-terminus of the first repeat was fused to the N-terminus of the second repeat, in yeast mitochondria. The tandem dimer was expressed in the mitochondrial membrane at the same level as that of yAAC2, being inserted into the mitochondrial membrane as in yAAC2, and it showed very similar transport activity to that of yAAC2. It was suggested that the two carrier molecules in a dimeric form are located in the membrane facing each other in the same orientation.