Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 105, Issue 10, Pages 4056-4061Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0710518105
Keywords
calvin cycle; photosynthesis; protein-protein interactions; redox
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Funding
- Biotechnology and Biological Sciences Research Council [P19403] Funding Source: Medline
- Biotechnology and Biological Sciences Research Council [P19403] Funding Source: researchfish
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A Calvin cycle multiprotein complex including phosphoribulokinase (PRK), glyceraidehyde-3-phosphate clehydrogenase (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.
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