Biogenesis of peroxisomes in the yeast Candida tropicalis pK233: Genes, proteins and organellar targeting

Abstract

<p>Related efforts resulted in the cloning of two genes (and one composite full-length cDNA) encoding different enzymes associated with the $\beta$-oxidation pathway of C. tropicalis peroxisomes. Sequencing of the gene encoding acyl-coenzyme A oxidase (AOx), revealed a single open reading frame, without intervening sequences, of 2,127 nucleotides which encodes a polypeptide of 709 amino acids (Mᵣ 79155). The deduced amino acid sequence of C. tropicalis AOx exhibits significant identity and homology with that of several other acyl-coenzyme A oxidases of C. tropicalis, as well as those of other yeasts (C. maltosa and S. cerevisiae) and rat. By comparison, sequencing of the C. tropicalis gene (or cDNA) encoding catalase (Cat) revealed a single open reading frame of 1,455 nucleotides, without intervening sequences, which encodes a polypeptide of 485 amino acids (Mᵣ 54944). The deduced amino acid sequence of C. tropicalis Cat shows significant identity and homology with that of catalases from the yeast S. cerevisiae, mammals (rat, human and bovine), plants (maize, sweet potato and cottonseed) and Drosophila. Studies concerned with the in vivo expression and targeting of Cat from C. tropicalis to the peroxisomes of C. albicans and S. cerevisiae were initiated. Subsequent determination of the subcellular location of the full-length Cat polypeptide suggested that Cat from C. tropicalis was targeted to the peroxisomes of S. cerevisiae, reaffirming that heterologous signals for import into peroxisomes are recognized in S. cerevisiae. Interestingly, the deletion of amino acids 182 to 344 of Cat negated the targeting of Cat to S. cerevisiae peroxisomes. These preliminary in vivo studies suggest that at least part of the PTS of Cat from C. tropicalis resides at an internal location within its mature amino acid sequence. (Abstract shortened by UMI.)</p>