Diatom Plastids Possess a Phosphoribulokinase with an Altered Regulation and No Oxidative Pentose Phosphate Pathway

Michels, Andreas K.; Wedel, Norbert; Kroth, Peter G.

doi:10.1104/pp.104.055285

Cited by 84 publications

(102 citation statements)

References 58 publications

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“…The lack of response of the pea PRK/GAPDH/CP12 complex to NADPH is not strictly consistent with all of the previous studies on this complex possibly because of differences in the techniques used to visualize the complex (15,16,25,27). Alternatively, this may reflect the differences in metabolic regulation between cyanobacteria, algae, and higher plants (25,(29)(30)(31)(32).…”

Section: Discussionmentioning

confidence: 57%

Thioredoxin-mediated reversible dissociation of a stromal multiprotein complex in response to changes in light availability

Howard

Metodiev

Lloyd

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

106

133

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A Calvin cycle multiprotein complex including phosphoribulokinase (PRK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and a small protein, CP12, has previously been identified. In this article, we have studied this complex in leaves and have shown that dissociation and reassociation of the PRK/GAPDH/CP12 complex occurs in a time frame of minutes, allowing for rapid regulation of enzyme activity. Furthermore, we have shown that the extent of formation and dissociation of the PRK/GAPDH/CP12 complex correlates with the quantity of light. These data provide evidence linking the status of this complex with the rapid and subtle regulation of GAPDH and PRK activities in response to fluctuations in light availability. We have also demonstrated that dissociation of this complex depends on electron transport chain activity and that the major factor involved in the dissociation of the pea complex was thioredoxin f. We show here that both PRK and GAPDH are present in the reduced form in leaves in the dark, but are inactive, demonstrating the role of the PRK/GAPDH/CP12 complex in deactivating these enzymes in response to reductions in light intensity. Based on our data, we propose a model for thioredoxin f-mediated activation of PRK and GAPDH by two mechanisms: directly through reduction of disulfide bonds within these enzymes and indirectly by mediating the breakdown of the complex in response to changes in light intensity.Calvin cycle ͉ photosynthesis ͉ protein-protein interactions ͉ redox

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Section: Discussionmentioning

confidence: 57%

Thioredoxin-mediated reversible dissociation of a stromal multiprotein complex in response to changes in light availability

Howard

Metodiev

Lloyd

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

106

133

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“…PRK is strongly regulated by thioredoxins in higher plants and green algae (Porter et al, 1988;Graciet et al, 2004), but apparently is less redox sensitive in cyanobacteria and diatoms (Kobayashi et al, 2003;Michels et al, 2005). GAPDH is finely regulated by thioredoxins, NAD(P)(H), and BPGA in higher plants (Pupillo and Giuliani Piccari, 1975;Wolosiuk and Buchanan, 1978;Trost et al, 1993;Baalmann et al, 1995;Sparla et al, 2002), but it does not appear to be regulated in lower photosynthetic organisms.…”

Section: Discussionmentioning

confidence: 99%

Reconstitution and Properties of the Recombinant Glyceraldehyde-3-Phosphate Dehydrogenase/CP12/Phosphoribulokinase Supramolecular Complex of Arabidopsis

et al. 2005

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Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) form together with the regulatory peptide CP12 a supramolecular complex in Arabidopsis (Arabidopsis thaliana) that could be reconstituted in vitro using purified recombinant proteins. Both enzyme activities were strongly influenced by complex formation, providing an effective means for regulation of the Calvin cycle in vivo. PRK and CP12, but not GapA (A4 isoform of GAPDH), are redox-sensitive proteins. PRK was reversibly inhibited by oxidation. CP12 has no enzymatic activity, but it changed conformation depending on redox conditions. GapA, a bispecific NAD(P)-dependent dehydrogenase, specifically formed a binary complex with oxidized CP12 when bound to NAD. PRK did not interact with either GapA or CP12 singly, but oxidized PRK could form with GapA/CP12 a stable ternary complex of about 640 kD (GapA/CP12/PRK). Exchanging NADP for NAD, reducing CP12, or reducing PRK were all conditions that prevented formation of the complex. Although GapA activity was little affected by CP12 alone, the NADPH-dependent activity of GapA embedded in the GapA/CP12/PRK complex was 80% inhibited in respect to the free enzyme. The NADH activity was unaffected. Upon binding to GapA/CP12, the activity of oxidized PRK dropped from 25% down to 2% the activity of the free reduced enzyme. The supramolecular complex was dissociated by reduced thioredoxins, NADP, 1,3-bisphosphoglycerate (BPGA), or ATP. The activity of GapA was only partially recovered after complex dissociation by thioredoxins, NADP, or ATP, and full GapA activation required BPGA. NADP, ATP, or BPGA partially activated PRK, but full recovery of PRK activity required thioredoxins. The reversible formation of the GapA/CP12/PRK supramolecular complex provides novel possibilities to finely regulate GapA (“non-regulatory” GAPDH isozyme) and PRK (thioredoxin sensitive) in a coordinated manner.

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“…In T. pseudonana, a cytosolic localization of the pyrimidine de novo synthesis similar to that of heterotrophs was suggested (3). Furthermore, the plastidial oxidative pentose phosphate pathway, which provides ribose-5-phosphate for nucleotide synthesis during dark phases in plant plastids, is not present in diatom plastids (4,14). Here, we identified that in a centric and a pennate diatom pyrimidine and purine nucleotides are generated in the cytosol.…”

mentioning

confidence: 80%

Diatom plastids depend on nucleotide import from the cytosol

Ast¹,

Gruber

Schmitz‐Esser

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

112

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Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms with primary plastids. Diatom plastids are surrounded by 4 membranes; the outermost membrane is continuous with the endoplasmic reticulum. Genome analyses suggest that nucleotide biosynthesis is, in contrast to higher plants, not located in the plastid, but in the cytosol. As a consequence, nucleotides have to be imported into the organelle. However, the mechanism of nucleotide entry into the complex plastid is unknown. We identified a high number of putative nucleotide transporters (NTTs) in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum and characterized the first 2 isoforms (NTT1 and NTT2). GFP-based localization studies revealed that both investigated NTTs are targeted to the plastid membranes, and that NTT1 most likely enters the innermost plastid envelope via the stroma. Heterologously expressed NTT1 acts as a proton-dependent adenine nucleotide importer, whereas NTT2 facilitates the counter exchange of (deoxy-)nucleoside triphosphates. Therefore, these transporters functionally resemble NTTs from obligate intracellular bacteria with an impaired nucleotide metabolism rather than ATP/ADP exchanging NTTs from primary plastids. We suggest that diatoms harbor a specifically-adapted nucleotide transport system and that NTTs are the key players in nucleotide supply to the complex plastid.chloroplast ͉ complex plastids ͉ nucleotide synthesis ͉ nucleotide transport

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Diatom Plastids Possess a Phosphoribulokinase with an Altered Regulation and No Oxidative Pentose Phosphate Pathway

Cited by 84 publications

References 58 publications

Thioredoxin-mediated reversible dissociation of a stromal multiprotein complex in response to changes in light availability

Thioredoxin-mediated reversible dissociation of a stromal multiprotein complex in response to changes in light availability

Reconstitution and Properties of the Recombinant Glyceraldehyde-3-Phosphate Dehydrogenase/CP12/Phosphoribulokinase Supramolecular Complex of Arabidopsis

Diatom plastids depend on nucleotide import from the cytosol

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