Dual Targeting of Yeast Catalase A to Peroxisomes and Mitochondria

Biochem J. 2004 Jun 1;380(Pt 2):393-400. doi: 10.1042/BJ20040042.

Abstract

Yeast catalase A (Cta1p) contains two peroxisomal targeting signals (SSNSKF) localized at its C-terminus and within the N-terminal third of the protein, which both can target foreign proteins to peroxisomes. In the present study we demonstrated that Cta1p can also enter mitochondria, although the enzyme lacks a classical mitochondrial import sequence. Cta1p co-targeting was studied in a catalase A null mutant after growth on different carbon sources, and expression of a Cta1p-GFP (green fluorescent protein)-fusion protein or a Cta1p derivative containing either a c-Myc epitope (Cta1p(myc)) or a SKF-extended tag (Cta1p(myc-SKF)). Peroxisomal and mitochondrial co-import of catalase A were tested qualitatively by fluorescence microscopy and functional complementation of a Delta cta1 null mutation, and quantitatively by subcellular fractionation followed by Western blot analysis and enzyme activity assays. Efficient Cta1p import into peroxisomes was observed when cells were cultivated under peroxisome-inducing conditions (i.e. growth on oleate), whereas significant co-import of Cta1p-GFP into mitochondria occurred when cells were grown under respiratory conditions that favour oxygen stress and ROS (reactive oxygen species) accumulation within this organelle. In particular, when cells were grown on the non-fermentable carbon source raffinose, respiration is maximally enhanced, and catalase A was efficiently targeted to the mitochondrial matrix where it presumably functions as scavenger of H2O2 and mitochondrial-derived ROS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalase / genetics
  • Catalase / metabolism*
  • Cell Fractionation
  • Genetic Vectors / genetics
  • Genetic Vectors / metabolism
  • Green Fluorescent Proteins
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Mitochondria / chemistry
  • Mitochondria / enzymology*
  • Peroxisomes / chemistry
  • Peroxisomes / enzymology*
  • Protein Sorting Signals / genetics
  • Protein Sorting Signals / physiology
  • Protein Transport / genetics
  • Protein Transport / physiology
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • Isoenzymes
  • Luminescent Proteins
  • Protein Sorting Signals
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Green Fluorescent Proteins
  • Catalase