Antibodies directed against a yeast carboxyl‐terminal peroxisomal targeting signal specifically recognize peroxisomal proteins from various yeasts

The carboxyl‐terminal tripeptide Ala‐Lys‐Ile is essential for targeting Canadida tropicalis trifunctional enzyme (hydratase‐dehydrogenase‐epimerase) to peroxisomes of both Candida albicans and Saccharomyces cerevisiae (Aitchison, J. D., Murray, W. W. and Rachubinski, R. A. (1991). J. Biol. Chem. 266, 23197–23203). We investigated the possibility that this tripeptide may act as a general peroxisomal targeting signal (PTS) for other proteins in the yeasts C. tropicalis, C. albicans, Yarrowia lipolytica and S. cerevisiae, and in rat liver. Anti‐AKI antibodies raised against the carboxyl‐terminal 12 amino acids of trifunctional enzyme were used to search for this PTS in proteins of these yeasts and of rat liver. The anti‐AKI antibodies reacted exclusively with multiple peroxisomal proteins from the yeasts C. tropicalis, C. albicans and Y. lipolytica. There was a weak reaction of the antibodies with one peroxisomal protein from S. cerevisiae and no reaction with peroxisomal proteins from rat liver. Antibodies directed against a synthetic peptide containing a carboxyl‐terminal Ser‐Lys‐Leu PTS (Gould, S. J., Krisans, S., Keller, G.‐A. and Subramani, S. (1990). J. Cell Biol. 110, 27–34) reacted with multiple peroxisomal proteins of rat liver and with peroxisomal proteins of yeast distinct from those identified with anti‐AKI antibodies. These results provide evidence that several peroxisomal proteins of different yeasts contain a PTS antigenically similar to that of C. tropicalis trifunctional enzyme and that this signal is absent from peroxisomal proteins from at least one mammalian system, rat liver.