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Chapitre D'ouvrage Année : 2022

The Assembly of Photosynthetic Proteins

Résumé

Photosynthetic energy transduction is performed by oligomeric proteins embedded in the thylakoid membranes. With the exception of the antenna complexes, which are exclusively comprised of nucleusencoded subunits, all photosynthetic complexes contain both nucleus-and chloroplast-encoded subunits. Thus, the two genetic compartments cooperate to produce these subunits in stoichiometries required for their functional assembly. The nucleus-encoded subunits of a complex are translated in the cytosol, imported into the chloroplast and then targeted to their site of assembly with subunits translated in the chloroplast. Assembly factors assist in folding these polypeptide subunits into an assembly-competent conformation. The pleiotropic loss of all subunits of a photosynthetic protein in Chlamydomonas mutants lacking expression of only one of the subunit has indicated that the assembly of each protein complex results from the concerted accumulation of the constituent subunits, which involves two major regulatory processes: proteolytic degradation of some unassembled subunits, and a down-regulation of translation of other chloroplast-encoded subunits when they are not properly assembled. This latter process has been designated CES (for Control by Epistasy of Synthesis). CES is a versatile regulatory process with modalities that may differ from one CES subunit to another, depending on the features associated with the biogenesis of the specific photosynthetic complex. Here we focus mainly on those studies in which Chlamydomonas has contributed new knowledge to the assembly of photosynthetic proteins. Thus, most of this chapter is devoted to the CES process because this microalga has been instrumental in its discovery, but later studies have shown that this process is key to the biogenesis of energy-transducing complexes in higher plant chloroplasts and yeast mitochondria. It probably evolved following the primary endosymbiotic event that led to the evolution of chloroplasts since CES does not occur in cyanobacteria.
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Dates et versions

hal-03941663 , version 1 (16-01-2023)

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  • HAL Id : hal-03941663 , version 1

Citer

Yves Choquet, Francis-André Wollman. The Assembly of Photosynthetic Proteins. Academic Press. The Chlamydomonas SourceBook, 3rd Edition, Volume 2 Organellar and Metabolics Processes, Arthur Grossman and Francis-André Wollman Editors, Volume 2 Organellar and Metabolics Processes, Arthur Grossman and Francis-André Wollman Editors, Elsevier, In press, 9780128214305. ⟨hal-03941663⟩
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