Expression of the bovine heart mitochondrial ADP/ATP carrier in yeast mitochondria: significantly enhanced expression by replacement of the N-terminal region of the bovine carrier by the corresponding regions of the yeast carriers.

To characterize the transport mechanism mediated by the mammalian mitochondrial ADP/ATP carrier (AAC), we tried to express bovine heart mitochondrial AAC (bhAAC) in Saccharomyces cerevisiae. The open reading frame of the bhAAC was introduced into the haploid strain WB-12, in which intrinsic AAC genes were disrupted. Growth of the transformant was very low in glycerol medium, and a little amount of bhAAC was detected in the mitochondrial membrane. For improvement of bhAAC expression in WB-12, we introduced DNA fragments encoding chimeric bhAACs, in which the N-terminal region of the bhAAC extending into the cytosol was replaced by the corresponding regions of the type 1 and type 2 yeast AAC isoforms (yAAC1 and yAAC2). These transformants grew well, and the amounts of the chimeric bhAACs in their mitochondria were as high as that of yAAC2. The carriers expressed showed essentially the same ADP transport activities as that of AAC in bovine heart mitochondria.