title: Arabidopsis thaliana mitochondrial EF-G1 functions in two different translation steps.
abstract: Translation elongation factor G (EF-G) in bacteria catalyses the translocation of transfer RNA on ribosomes in the elongation step as well as dissociation of post-termination state ribosomes into two subunits in the recycling step. In contrast, the dual functions of EF-G are exclusively divided into two different paralogues in human mitochondria, named EF-G1mt for translocation and EF-G2mt for ribosomal dissociation. Many of the two eukaryotic EF-G paralogues are phylogenetically associated with EF-G1mt and EF-G2mt groups. However, plant paralogues are associated with EF-G1mt and plastid EF-G, not with EF-G2mt. In this study, we phylogenetically and biochemically characterized Arabidopsis thaliana EF-G1mt (AtEF-G1mt) to clarify the factor responsible for the dissociation of ribosomes in plant mitochondria. We showed that eukaryotic EF-G1mts form one monophyletic group separated from bacterial EF-G and are classified into five sister groups. AtEF-G1mt is classified into a different group from its human counterpart. We also demonstrated that AtEF-G1mt catalyses both translocation and ribosomal dissociation, unlike in humans. Meanwhile, AtEF-G1mt is resistant to fusidic acid, an inhibitor of bacterial EF-G. Here, we propose that the functional division is not necessarily conserved among mitochondriate eukaryotes and also that EF-G1mt in organisms lacking EF-G2mt functions in two steps, similar to conventional bacterial EF-G.
authors.affiliation: Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, and Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji-shi, Tokyo 192-0392, Japan.
authors.forename: Takuma
authors.initials: T
authors.lastname: Suematsu
authors.forename: Osamu
authors.initials: O
authors.lastname: Watanabe
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kita
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yokobori
authors.forename: Yoh-ichi
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D017360:Arabidopsis / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D005672:Fusidic Acid / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D020653:Peptide Elongation Factor G / Q000502:physiology*; D010802:Phylogeny; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
chemical_list: D020653:Peptide Elongation Factor G; D011500:Protein Synthesis Inhibitors; D005672:Fusidic Acid; D020558:GTP Phosphohydrolases
keywords: Arabidopsis thaliana; EF-G; mitochondria; ribosome recycling factor; translation