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Structure, fonction et évolution de la famille universelle Sua5/YrdC impliquée dans la synthèse du nucléoside modifié t6A

Abstract : Structure, function and evolution of the universal Sua5/YrdC family involved in the modified nucleoside t6A synthesist6A is universally found in tRNAs that read ANN codons and is essential for translation fidelity. Its synthesis takes place in two stages, the first one involving the formation of the reaction intermediate Threonyl-Carbamoyl-AMP (TC-AMP) by the Sua5/YrdC family. This family is found in all organisms and was thus presumably presents in the Last Universal Common Ancestor (LUCA). It’s composed of two distinct variants, YrdC and Sua5, which share an orthologous catalytic domain. While YrdC is a single domain protein, Sua5 has an additional C-terminal domain of unknown function named SUA5. Most species encode for either variant and both variants are found in the three domains of life, Eukarya, Archaea and Bacteria. To discover the role of the SUA5 domain and the inter-domain linker, we studied the Sua5 protein from the archaeon Pyrococcus abyssi. We found that they are both important for the activity of Sua5. The linker is able to control the entry and exit of ligands by changing conformation while the SUA5 domain acts as an anchoring platform for the linker. To understand the evolutionary history of the Sua5/YrdC family, we then studied the distribution of Sua5 and YrdC across the tree of life and we used in silico and in vitro approaches to identify functional differences between YrdC and Sua5. Taken together, our work allows us to propose that LUCA encoded a Sua5 protein and that YrdC emerged after domain loss in some lineages during evolution.
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Adeline Pichard. Structure, fonction et évolution de la famille universelle Sua5/YrdC impliquée dans la synthèse du nucléoside modifié t6A. Biochimie, Biologie Moléculaire. Université Paris Saclay (COmUE), 2017. Français. ⟨NNT : 2017SACLS371⟩. ⟨tel-02724874⟩

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