Molecular characterization of carnitine-dependent transport of acetyl-CoA from peroxisomes to mitochondria in Saccharomyces cerevisiae and identification of a plasma membrane carnitine transporter, Agp2p

In Saccharomyces cerevisiae, beta-oxidation of fatty acids is confined to p eroxisomes. The acetyl-CoA produced has to be transported from the peroxiso mes via the cytoplasm to the mitochondrial matrix in order to be degraded t o CO2 and H2O. Two pathways for the transport of acetyl-CoA to the mitochon dria have been proposed. The first involves peroxisomal conversion of acety l-CoA into glyoxylate cycle intermediates followed by transport of these in termediates to the mitochondria. The second pathway involves peroxisomal co nversion of acetyl-CoA into acetylcarnitine, which is subsequently transpor ted to the mitochondria. Using a selective screen, we have isolated several mutants that are specifically affected in the second pathway, the carnitin e-dependent acetyl-CoA transport from the peroxisomes to the mitochondria, and assigned these CDAT mutants to three different complementation groups. The corresponding genes were identified using functional complementation of the mutants with a genomic DNA library In addition to the previously repor ted carnitine acetyl-CoA transferase (CAT2), we identified the genes for th e yeast orthologue of the human mitochondrial carnitine acylcarnitine trans locase (YOR100C or CAC) and for a transport protein (AGP2) required for car nitine transport across the plasma membrane.