PMID:11717467

Citation	Laloi, C, Rayapuram, N, Chartier, Y, Grienenberger, JM, Bonnard, G and Meyer, Y (2001) Identification and characterization of a mitochondrial thioredoxin system in plants. Proc. Natl. Acad. Sci. U.S.A. 98:14144-9
Abstract	Plants possess two well described thioredoxin systems: a cytoplasmic system including several thioredoxins and an NADPH-dependent thioredoxin reductase and a specific chloroplastic system characterized by a ferredoxin-dependent thioredoxin reductase. On the basis of biochemical activities, plants also are supposed to have a mitochondrial thioredoxin system as described in yeast and mammals, but no gene encoding plant mitochondrial thioredoxin or thioredoxin reductase has been identified yet. We report the characterization of a plant thioredoxin system located in mitochondria. Arabidopsis thaliana genome sequencing has revealed numerous thioredoxin genes among which we have identified AtTRX-o1, a gene encoding a thioredoxin with a potential mitochondrial transit peptide. AtTRX-o1 and a second gene, AtTRX-o2, define, on the basis of the sequence and intron positions, a new thioredoxin type up to now specific to plants. We also have characterized AtNTRA, a gene encoding a protein highly similar to the previously described cytosolic NADPH-dependent thioredoxin reductase AtNTRB but with a putative presequence for import into mitochondria. Western blot analysis of A. thaliana subcellular and submitochondrial fractions and in vitro import experiments show that AtTRX-o1 and AtNTRA are targeted to the mitochondrial matrix through their cleavable N-terminal signal. The two proteins truncated to the estimated mature forms were produced in Escherichia coli; AtTRX-o1 efficiently reduces insulin in the presence of DTT and is reduced efficiently by AtNTRA and NADPH. Therefore, the thioredoxin and the NADPH-dependent thioredoxin reductase described here are proposed to constitute a functional plant mitochondrial thioredoxin system.
Links	PubMed PMC61182 Online version:10.1073/pnas.241340898
Keywords	Amino Acid Sequence; Arabidopsis/genetics; Arabidopsis Proteins; Base Sequence; Biological Transport; DNA, Plant; Enzyme Activation; Enzyme Precursors/metabolism; Genes, Plant; Mitochondria/metabolism; Molecular Sequence Data; Peptides/genetics; Peptides/metabolism; Plant Proteins/classification; Plant Proteins/genetics; Plant Proteins/metabolism; Protein Precursors/metabolism; Subcellular Fractions; Thioredoxin h; Thioredoxin-Disulfide Reductase/genetics; Thioredoxin-Disulfide Reductase/metabolism; Thioredoxins/classification; Thioredoxins/genetics; Thioredoxins/metabolism
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