A specific form of thioredoxin h occurs in plant mitochondria and regulates the alternative oxidase

• DOI: 10.1073/pnas.0405282101
• Publication Date: 2004-09-23T00:24:01Z
• Authors: Eric Gelhaye; Nicolas Rouhier; Joelle Gérard; Yves Jolivet; José Gualberto; Nicolas Navrot; Per-Ingvard Ohlsson; Gunnar Wingsle; Masakazu Hirasawa; David B. Knaff; Hongmei Wang; Pierre Dizengremel; Yves Meyer; Jean-Pierre Jacquot
• Keywords: 0301 basic medicine; 2. Zero hunger; Glutathione Peroxidase; Base Sequence; Recombinant Fusion Proteins; Thioredoxin h; DNA, Recombinant; [SDV.BC]Life Sciences [q-bio]/Cellular Biology; Plants; Plants, Genetically Modified; Mitochondria; GLUTATIONE PEROXYDASE; Mitochondrial Proteins; 03 medical and health sciences; Populus; PEUPLIER; Oxidoreductases; [SDV.BC] Life Sciences [q-bio]/Cellular Biology; Oxidation-Reduction; Phylogeny; Plant Proteins

The plant mitochondrial thioredoxin (Trx) system has been described as containing an NADPH-dependent Trx reductase and Trx o . In addition to the mitochondrial isoform, Trx o , plants are known to contain several chloroplastic Trx isoforms and the cytosolic Trx h isoforms. We report here the presence in plant mitochondria of a Trx isoform (PtTrx h 2) belonging to the Trx h group. Western blot analyses with mitochondrial proteins isolated from both poplar and GFP fusion constructs indicate that PtTrx h 2 is targeted to plant mitochondria. The recombinant protein, PtTrx h 2, has been shown to be reduced efficiently by the mitochondrial Trx reductase AtNTRA. PtTrx h 2 is also able to reduce alternative oxidase homodimers and to allow its activation by pyruvate. In contrast, neither PtTrx h 2 nor AtTrx o 1 exhibits activity with several poplar glutathione peroxidases and especially a putative mitochondrial isoform. Incubation of PtTrx h 2 with glutathione disulfide led to the formation of glutathionylated Trx, identified by mass spectrometry. The formation of a glutathione adduct increases the redox potential of PtTrx h 2 from -290 to -225 mV. In addition to Trx o , this study shows that Trx h could also be present in mitochondria. This previously unrecognized complexity is not unexpected, considering the multiple redox-regulated processes found in plant mitochondria.