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

Abstract

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

Antisense Suppression of the Small Chloroplast Protein CP12 in Tobacco Alters Carbon Partitioning and Severely Restricts Growth

“…Support for the importance of CP12 in mediating the formation of this complex has come from in vitro experiments utilizing recombinant expressed proteins or partially purified components. These data have demonstrated that complex formation is dependent upon the presence of oxidized CP12 (Scheibe et al, 2002;Marri et al, 2005), and recent evidence suggests that this is mediated by changes in the redox state of thioredoxin f (Howard et al, 2008;Marri et al, 2009).…”

“…This complex has been shown to be present in several higher plant species (Wedel et al, 1997;Wedel and Soll, 1998;Scheibe et al, 2002;Howard et al, 2011), in algal species (Avilan et al, 1997;Boggetto et al, 2007;Oesterhelt et al, 2007), and in a cyanobacterium (Tamoi et al, 2005). Furthermore, dissociation and aggregation of this complex in pea (Pisum sativum) leaves are rapid and respond to light quantity (Howard et al, 2008). Support for the importance of CP12 in mediating the formation of this complex has come from in vitro experiments utilizing recombinant expressed proteins or partially purified components.…”

Comparative Analysis of 126 Cyanobacterial Genomes Reveals Evidence of Functional Diversity Among Homologs of the Redox-Regulated CP12 Protein

“…This is interesting because, as in higher plants, the formation and breakdown of the PRK-GAPDH complex is mediated by the redox state of CP12, which in turn is mediated by thioredoxin (Howard et al, 2008;Marri et al, 2009).…”

“…The formation of the GAPDH-PRK-CP12 complex inhibits GAPDH and PRK activity leading to down-regulation of the Calvin cycle; this has been demonstrated in plants, Chlamydomonas reinhardtii, and cyanobacteria (Wedel et al, 1997;Graciet et al, 2003a;Marri et al, 2005b;Tamoi et al, 2005). The GAPDH-PRK-CP12 complex dissociates under reducing conditions mediated by thioredoxin, thereby restoring GAPDH and PRK activity (Lebreton et al, 2003;Marri et al, 2005bMarri et al, , 2009Howard et al, 2008). Erales et al (2008a) showed that CP12 binds aldolase, another Calvin cycle enzyme, implying the involvement of CP12 in additional Calvin cycle regulation.…”

“…In eukaryotic organisms, CP12 is located in the chloroplast, where the only function thus far identified is in the regulation of the Calvin cycle in response to changes in light availability by reversibly binding glyceraldehyde-3-P dehydrogenase (GAPDH) and, subsequently, phosphoribulokinase (PRK; Wedel et al, 1997;Graciet et al, 2003aGraciet et al, , 2003bMarri et al, 2005aMarri et al, , 2008Erales et al, 2008a;Howard et al, 2008;Carmo-Silva et al, 2011). The formation of the GAPDH-PRK-CP12 complex inhibits GAPDH and PRK activity leading to down-regulation of the Calvin cycle; this has been demonstrated in plants, Chlamydomonas reinhardtii, and cyanobacteria (Wedel et al, 1997;Graciet et al, 2003a;Marri et al, 2005b;Tamoi et al, 2005).…”