Cytochrome f translation in Chlamydomonas chloroplast is autoregulated by its carboxyl-terminal domain |
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Authors: | Choquet Yves Zito Francesca Wostrikoff Katia Wollman Francis-André |
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Affiliation: | Centre National de la Recherche Scientifique Unité Propre de Recherche 1261, Institut de Biologie Physico-Chimique, F-75005 Paris, France. choquet@ibpc.fr |
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Abstract: | The rate of synthesis of cytochrome f is decreased approximately 10-fold when it does not assemble with the other subunits of the cytochrome b(6)f complex in Chlamydomonas reinhardtii chloroplasts. This assembly-mediated regulation of cytochrome f synthesis corresponds to a regulation of petA mRNA initiation of translation. Here, we demonstrate that cytochrome f translation is autoregulated by its C-terminal domain. Five cytochrome f residues conserved throughout all chloroplast genomes-residue Gln-297 in the transmembrane helix and a cluster of four amino acids, Lys-Gln-Phe-Glu, at positions 305 to 308, in the stromal extension-participate in the formation of a translation repressor motif. By contrast, positively charged residues in the stromal extension have little influence on the autoregulation process. These results do not favor a direct interaction between the repressor motif and the petA 5' untranslated region but suggest the participation of a membrane-bound ternary effector. |
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