INDIVIDUAL EXPRESSION OF CANDIDA-TROPICALIS PEROXISOMAL AND MITOCHONDRIAL CARNITINE ACETYLTRANSFERASE-ENCODING GENES AND SUBCELLULAR-LOCALIZATION OF THE PRODUCTS IN SACCHAROMYCES-CEREVISIAE

In an n-alkane-assimilating yeast, Candida tropicalis, carnitine acety ltransferase (CAT; EC 2.3.1.7) was localized in both peroxisomes and m itochondria. Both CATs were encoded by one gene, CT-CAT, although the initiation sites of translation were suggested to be different. In the present study, the genes corresponding ao the supposed C. tropicalis peroxisomal and mitochondrial CATs, which were truncated from the CT-C AT gene, were individually expressed in Saccharomyces cerevisiae, usin g the C. tropicalis isocitrate lyase promoter (UPR-ICL), which is indu cible by oleic acid in concert with proliferation of peroxisomes in S. cerevisiae [Umemura, K., Atomi, H., Kanai, T., Teranishi, Y., Ueda, M ., and Tanaka, A. (1995) Appl. Microbiol. Biotechnol. 43, 489-492]. Th e 71 kDa precursor of mitochondrial CAT, initiating at the first Met, was found to be processed to the mature size (66 kDa) in S. cerevisiae and immunoelectronmicroscopical observation revealed that this enzyme was localized in mitochondria. On the other hand, 68 kDa CAT, initiat ing at the second Met (residue No. 19), had no cleavable signal and wa s translocated into peroxisomes and cytosol, but not into mitochondria . The amino-terminal amino acid sequences of individually expressed CA Ts were identical to those of CATs isolated from alkane-grown C. tropi calis cells, respectively. These results demonstrated that only the 71 kDa protein yielded the 66 kDa protein and that peroxisomal and mitoc hondrial CATs arose from the difference in the initiation sites of tra nslation.