title: EF-G2mt is an exclusive recycling factor in mammalian mitochondrial protein synthesis.
abstract: Bacterial translation elongation factor G (EF-G) catalyzes translocation during peptide elongation and mediates ribosomal disassembly during ribosome recycling in concert with the ribosomal recycling factor (RRF). Two homologs of EF-G have been identified in mitochondria from yeast to man, EF-G1mt and EF-G2mt. Here, we demonstrate that the dual function of bacterial EF-G is divided between EF-G1mt and EF-G2mt in human mitochondria (RRFmt). EF-G1mt specifically catalyzes translocation, whereas EF-G2mt mediates ribosome recycling with human mitochondrial RRF but lacks translocation activity. Domain swapping experiments suggest that the functional specificity for EF-G2mt resides in domains III and IV. Furthermore, GTP hydrolysis by EF-G2mt is not necessary for ribosomal splitting, in contrast to the bacterial-recycling mode. Because EF-G2mt represents a class of translational GTPase that is involved in ribosome recycling, we propose to rename this factor mitochondrial ribosome recycling factor 2 (RRF2mt).
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tsuboi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morita
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nozaki
authors.forename: Kenta
authors.initials: K
authors.lastname: Akama
authors.forename: Takuya
authors.initials: T
authors.lastname: Ueda
authors.forename: Koichi
authors.initials: K
authors.lastname: Ito
authors.forename: Knud H
authors.initials: KH
authors.lastname: Nierhaus
authors.forename: Nono
authors.initials: N
authors.lastname: Takeuchi
mesh_terms: D000818:Animals; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010441:Peptide Chain Elongation, Translational; D020653:Peptide Elongation Factor G / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013552:Swine
chemical_list: C441681:GFM2 protein, human; D024101:Mitochondrial Proteins; D020653:Peptide Elongation Factor G; D011994:Recombinant Proteins; D012269:Ribosomal Proteins; C087267:ribosome releasing factor; D006160:Guanosine Triphosphate