The Arabidopsis plastidial thioredoxins: new functions and new insights into specificity

The sequencing of the genome of Arabidopsis thaliana revealed that this plant contained numerous isoforms of thioredoxin (Trx), a protein involved in thiol-disulfide exchanges. On the basis of sequence comparison, seven putative chloroplastic Trxs have been identified, four belonging to the m-type,...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-06, Vol.278 (26), p.23747-23752
Main Authors: Collin, Valerie, Issakidis-Bourguet, Emmanuelle, Marchand, Christophe, Hirasawa, Masakazu, Lancelin, Jean-Marc, Knaff, David B, Miginiac-Maslow, Myroslawa
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Arabidopsis - chemistry
Arabidopsis - ultrastructure
Arabidopsis Proteins - chemistry
Arabidopsis Proteins - metabolism
Fructose-Bisphosphatase - metabolism
Kinetics
Malate Dehydrogenase (NADP+)
Malate Dehydrogenase - metabolism
Models, Molecular
Molecular Sequence Data
Peroxidases - metabolism
Peroxiredoxins
Plastids - chemistry
Protein Isoforms - chemistry
Protein Isoforms - isolation & purification
Protein Isoforms - metabolism
Recombinant Proteins - chemistry
Recombinant Proteins - isolation & purification
Recombinant Proteins - metabolism
Sequence Alignment
Substrate Specificity
Thioredoxins - chemistry
Thioredoxins - isolation & purification
Thioredoxins - metabolism
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Summary:The sequencing of the genome of Arabidopsis thaliana revealed that this plant contained numerous isoforms of thioredoxin (Trx), a protein involved in thiol-disulfide exchanges. On the basis of sequence comparison, seven putative chloroplastic Trxs have been identified, four belonging to the m-type, two belonging to the f-type, and one belonging to a new x-type. In the present work, these isoforms were produced and purified as recombinant proteins without their putative transit peptides. Their activities were tested with two known chloroplast thioredoxin targets: NADP-malate dehydrogenase and fructose-1,6-bisphosphatase and also with a chloroplastic 2-Cys peroxiredoxin. The study confirms the strict specificity of fructose-bisphosphatase for Trx f, reveals that some Trxs are unable to activate NADP-malate dehydrogenase, and shows that the new x-type is the most efficient substrate for peroxiredoxin while being inactive toward the two other targets. This suggests that this isoform might be specifically involved in resistance against oxidative stress. Three-dimensional modeling shows that one of the m-type Trxs, Trx m3, which has no activity with any of the three targets, exhibits a negatively charged surface surrounding the active site. A green fluorescent protein approach confirms the plastidial localization of these Trxs.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M302077200