title: Atypical thioredoxins in poplar: the glutathione-dependent thioredoxin-like 2.1 supports the activity of target enzymes possessing a single redox active cysteine.
abstract: Plant thioredoxins (Trxs) constitute a complex family of thiol oxidoreductases generally sharing a WCGPC active site sequence. Some recently identified plant Trxs (Clot, Trx-like1 and -2, Trx-lilium1, -2, and -3) display atypical active site sequences with altered residues between the two conserved cysteines. The transcript expression patterns, subcellular localizations, and biochemical properties of some representative poplar (Populus spp.) isoforms were investigated. Measurements of transcript levels for the 10 members in poplar organs indicate that most genes are constitutively expressed. Using transient expression of green fluorescent protein fusions, Clot and Trx-like1 were found to be mainly cytosolic, whereas Trx-like2.1 was located in plastids. All soluble recombinant proteins, except Clot, exhibited insulin reductase activity, although with variable efficiencies. Whereas Trx-like2.1 and Trx-lilium2.2 were efficiently regenerated both by NADPH-Trx reductase and glutathione, none of the proteins were reduced by the ferredoxin-Trx reductase. Only Trx-like2.1 supports the activity of plastidial thiol peroxidases and methionine sulfoxide reductases employing a single cysteine residue for catalysis and using a glutathione recycling system. The second active site cysteine of Trx-like2.1 is dispensable for this reaction, indicating that the protein possesses a glutaredoxin-like activity. Interestingly, the Trx-like2.1 active site replacement, from WCRKC to WCGPC, suppresses its capacity to use glutathione as a reductant but is sufficient to allow the regeneration of target proteins employing two cysteines for catalysis, indicating that the nature of the residues composing the active site sequence is crucial for substrate selectivity/recognition. This study provides another example of the cross talk existing between the glutathione/glutaredoxin and Trx-dependent pathways.
authors.affiliation: UMR 1136 Lorraine University-INRA, Interactions Arbres-Microorganismes, Institut Fédératif de Recherche 110 Ecosystèmes Forestiers, Agroressources, Bioprocédés, et Alimentation, Faculté des Sciences, Vandoeuvre-lès-Nancy, France.
authors.forename: Kamel
authors.initials: K
authors.lastname: Chibani
authors.forename: Lionel
authors.initials: L
authors.lastname: Tarrago
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Gualberto
authors.forename: Gunnar
authors.initials: G
authors.lastname: Wingsle
authors.forename: Pascal
authors.initials: P
authors.lastname: Rey
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jacquot
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rouhier
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D020134:Catalytic Domain; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000737:chemistry; D004789:Enzyme Activation; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D054477:Glutaredoxins / Q000737:chemistry / Q000235:genetics; D005978:Glutathione / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000737:chemistry; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018087:Plastids / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
chemical_list: D060365:Chloroplast Proteins; D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; D010940:Plant Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D013879:Thioredoxins; D009249:NADP; D004228:Dithionitrobenzoic Acid; D010088:Oxidoreductases; C021588:ferredoxin-thioredoxin reductase; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione; D003545:Cysteine