title: Distinct electron transfer from ferredoxin-thioredoxin reductase to multiple thioredoxin isoforms in chloroplasts.
abstract: Thiol-based redox regulation is considered to support light-responsive control of various chloroplast functions. The redox cascade via ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) has been recognized as a key to transmitting reducing power; however,Arabidopsis thalianagenome sequencing has revealed that as many as five Trx subtypes encoded by a total of 10 nuclear genes are targeted to chloroplasts. Because each Trx isoform seems to have a distinct target selectivity, the electron distribution from FTR to multiple Trxs is thought to be the critical branch point for determining the consequence of chloroplast redox regulation. In the present study, we aimed to comprehensively characterize the kinetics of electron transfer from FTR to 10 Trx isoforms. We prepared the recombinant FTR protein fromArabidopsisin the heterodimeric form containing the Fe-S cluster. By reconstituting the FTR/Trx systemin vitro, we showed that FTR prepared here was enzymatically active and suitable for uncovering biochemical features of chloroplast redox regulation. A series of redox state determinations using the thiol-modifying reagent, 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonate, indicated that all chloroplast Trx isoforms are commonly reduced by FTR; however, significantly different efficiencies were evident. These differences were apparently correlated with the distinct midpoint redox potentials among Trxs. Even when the experiments were performed under conditions of hypotheticalin vivostoichiometry of FTR and Trxs, a similar trend in distinguishable electron transfers was observed. These data highlight an aspect of highly organized circuits in the chloroplast redox regulation network.
authors.affiliation: Laboratory for Chemistry and Life Science, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan yoshida.k.ao@m.titech.ac.jp thisabor@res.titech.ac.jp.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Laboratory for Chemistry and Life Science, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan yoshida.k.ao@m.titech.ac.jp thisabor@res.titech.ac.jp.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis / Q000187:drug effects; D020134:Catalytic Domain; D054479:Chloroplast Thioredoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013267:Stilbenes / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013451:Sulfonic Acids / Q000494:pharmacology
chemical_list: C000618862:4-acetamido-4'-maleimidylstilbene-2,2'-disulfonate; D029681:Arabidopsis Proteins; D054479:Chloroplast Thioredoxins; D007506:Iron-Sulfur Proteins; D010446:Peptide Fragments; D020033:Protein Isoforms; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013267:Stilbenes; D013439:Sulfhydryl Reagents; D013451:Sulfonic Acids; C000590496:TRX m4 protein, Arabidopsis; D010088:Oxidoreductases; C021588:ferredoxin-thioredoxin reductase
keywords: Arabidopsis thaliana; chloroplast; ferredoxin–thioredoxin reductase (FTR); redox regulation; thioredoxin (Trx)