title: Cytochrome f translation in Chlamydomonas chloroplast is autoregulated by its carboxyl-terminal domain.
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.
authors.affiliation: Centre National de la Recherche Scientifique Unité Propre de Recherche 1261, Institut de Biologie Physico-Chimique, F-75005 Paris, France. choquet@ibpc.fr
authors.forename: Yves
authors.initials: Y
authors.lastname: Choquet
authors.forename: Francesca
authors.initials: F
authors.lastname: Zito
authors.forename: Katia
authors.initials: K
authors.lastname: Wostrikoff
authors.forename: Francis-André
authors.initials: FA
authors.lastname: Wollman
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D002696:Chlamydomonas / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism*; D045348:Cytochromes f; D005786:Gene Expression Regulation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D014176:Protein Biosynthesis; D017386:Sequence Homology, Amino Acid; D020524:Thylakoids / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D003580:Cytochromes; D008565:Membrane Proteins; D045348:Cytochromes f