Peroxisomal and mitochondrial carnitine acetyltransferases of Saccharomyces cerevisiae are encoded by a single gene.
Carnitine acetyltransferase (CAT) is present in mitochondria and peroxisomes of oleate-grown Saccharomyces cerevisiae. Both proteins are encoded by the same gene, YCAT, which encodes a protein with a mitochondrial targeting signal (MTS) at the N-terminus, and a peroxisomal targeting signal type 1 (PTS-1) at the C-terminus. Deletion of both motifs revealed the presence of an additional internal targeting sequence. Import of CAT via this internal signal was shown to be dependent on PAS10, a protein which is required for the import of PTS-1 containing proteins. An interaction of PAS10 with this internal targeting signal was demonstrated using the yeast two-hybrid technique. Expression of the YCAT gene behind a heterologous promoter resulted in loss of peroxisomal targeting, indicating that differential targeting is controlled at transcriptional or translational level. Determination of the 5'-ends of YCAT mRNAs revealed that YCAT transcripts initiating after the first AUG were present in oleate-grown cells. These transcripts were virtually absent in acetate- or glycerol-grown cells. We propose that in response to oleate, shorter transcripts are produced from which the peroxisomal form of CAT is translated, resulting in a CAT protein without a MTS, which can be targeted to peroxisomes.
Elgersma
Y
Y
Department of Biochemistry, E.C. Slater Institute, Amsterdam, The Netherlands.
van Roermund
C W
CW
Wanders
R J
RJ
Tabak
H F
HF
D001483:Base Sequence; D002332:Carnitine O-Acetyltransferase / Q000235:genetics* / Q000378:metabolism; D017931:DNA Primers; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008830:Microbodies / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D015398:Signal Transduction; D014158:Transcription, Genetic
D017931:DNA Primers; D009829:Oleic Acids; D021382:Protein Sorting Signals; D019301:Oleic Acid; D002332:Carnitine O-Acetyltransferase