High-Resolution Crystal Structure of Chloroplastic Ribose-5-Phosphate Isomerase from Chlamydomonas reinhardtii—An Enzyme Involved in the Photosynthetic Calvin-Benson Cycle

Théo Le Moigne (1, 2, 3) , Pierre Crozet (1, 2, 4) , Stéphane Lemaire (1, 2, 5, 6) , Julien Henri (1, 2)

1 LBMCE - Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes
2 IBPC (FR_550) - Institut de biologie physico-chimique
3 IPS2 (UMR_9213 / UMR_1403) - Institut des Sciences des Plantes de Paris-Saclay
4 Polytech'Paris - Sorbonne Université
5 LCQB - Biologie Computationnelle et Quantitative = Laboratory of Computational and Quantitative Biology
6 IBPS - Institut de Biologie Paris Seine

The Calvin–Benson cycle is the key metabolic pathway of photosynthesis responsible for carbon fixation and relies on eleven conserved enzymes. Ribose-5-phosphate isomerase (RPI) isomerizes ribose-5-phosphate into ribulose-5-phosphate and contributes to the regeneration of the Rubisco substrate. Plant RPI is the target of diverse post-translational modifications including phosphorylation and thiol-based modifications to presumably adjust its activity to the photosynthetic electron flow. Here, we describe the first experimental structure of a photosynthetic RPI at 1.4 Å resolution. Our structure confirms the composition of the catalytic pocket of the enzyme. We describe the homo-dimeric state of the protein that we observed in the crystal and in solution. We also map the positions of previously reported post-translational modifications and propose mechanisms by which they may impact the catalytic parameters. The structural data will inform the biochemical modeling of photosynthesis.

Mots clés: Calvin–Benson cycle; X-ray crystallography; chloroplast; oligomerization; photosynthesis; post-translational modification; protein complexes; protein structure; redox; ribose isomerase

Domaines: Biologie structurale [q-bio.BM]

Théo Le Moigne, Pierre Crozet, Stéphane Lemaire, Julien Henri. High-Resolution Crystal Structure of Chloroplastic Ribose-5-Phosphate Isomerase from Chlamydomonas reinhardtii—An Enzyme Involved in the Photosynthetic Calvin-Benson Cycle. International Journal of Molecular Sciences, 2020, 21 (20), pp.7787. ⟨10.3390/ijms21207787⟩. ⟨hal-03011590⟩