Dual targeting of yeast catalase A to peroxisomes and mitochondria

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.

A Comparative Proteomic Strategy for Subcellular Proteome Research

“…Especially, protein catalse and AP endonuclease 1, which have been known as peroxisomal and nuclear, respectively, have shown a ratio of PM:CM Ͼ1.0 (1.41 Ϯ 0.26 and 4.55, respectively) (Supplemental Figs. 1 and 2), confirming the reports about their mitochondrial location (37,(53)(54)(55)(56). Functional study of those proteins will promote our understanding on mitochondria structure and function.…”

“…AP endonuclease 1 and catalase, which have been predicted as nonmitochondrial proteins by all five bioinformatics tools, have a ratio of PM:CM as 4.55 and 1.41 Ϯ 0.26, respectively. All four proteins have been annotated as mitochondria-associated multilocation proteins according to Swiss-Prot database or literature reports (37,(53)(54)(55)(56).…”

“…It has been more recently demonstrated that Cta1p can also enter mitochondria, although the enzyme lacks a classical mitochondrial import sequence. Peroxisomal and mitochondrial coimport of catalase A were tested qualitatively by fluorescence microscopy and functional complementation of a ⌬cta1 null mutation, and quantitatively by subcellular fractionation followed by Western analysis and enzyme activity assays (54). More interestingly, in the proteomic analysis of the rat liver peroxisome obtained by differential centrifugation and further purified by density gradient and by immunopurification, according to the SDS-PAGE band intensity, the amount of the most abundant matrix protein, catalase, seemed to decrease, while the band corresponding to another major matrix protein, uricase, clearly increased in its intensity (37).…”

Plant organellar protein targeting: a traffic plan still under construction

“…Catalase A is efficiently targeted to the peroxisome when the cells are grown on oleate. However, in spite of the apparent absence of a presequence, the protein is localized to the mitochondrial matrix when the cells are enhanced in respiration by growth on the non-fermentable carbon source raffinose [35]. These cellular-responsive dual distributions can be highly disparate in their relative levels, a phenomenon termed eclipsed distributions; this is the case for aconitase in the cytosol and the mitochondrion [36].…”

Caracterização do papel da glutamil-tRNA sintetase na localização subcelular de proteínas

“…Entretanto, mesmo na ausência de uma pré-sequência, a proteína pode localizar-se na matriz mitocondrial quando as células de levedura crescem em fonte de carbono não-fermentável (PETROVA et al, 2004).…”