Chaperone properties of mammalian mitochondrial translation elongation factor Tu.
The main function of the prokaryotic translation elongation factor Tu (EF-Tu) and its eukaryotic counterpart eEF1A is to deliver aminoacyl-tRNA to the A-site on the ribosome. In addition to this primary function, it has been reported that EF-Tu from various sources has chaperone activity. At present, little information is available about the chaperone activity of mitochondrial EF-Tu. In the present study, we have examined the chaperone function of mammalian mitochondrial EF-Tu (EF-Tumt). We demonstrate that recombinant EF-Tumt prevents thermal aggregation of proteins and enhances protein refolding in vitro and that this EF-Tumt chaperone activity proceeds in a GTP-independent manner. We also demonstrate that, under heat stress, the newly synthesized peptides from the mitochondrial ribosome specifically co-immunoprecipitate with EF-Tumt and are destabilized in EF-Tumt-overexpressing cells. We show that most of the EF-Tumt localizes on the mitochondrial inner membrane where most mitochondrial ribosomes are found. We discuss the possible role of EF-Tumt chaperone activity in protein quality control in mitochondria, with regard to the recently reported in vivo chaperone function of eEF1A.
Suzuki
Hiroaki
H
Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Building FSB-401, 5-1-5, Kashiwa, Chiba Prefecture 277-8562, Japan.
Ueda
Takuya
T
Taguchi
Hideki
H
Takeuchi
Nono
N
D000818:Animals; D002417:Cattle; D002460:Cell Line; D006160:Guanosine Triphosphate / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000502:physiology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D010444:Peptide Elongation Factor Tu / Q000235:genetics / Q000502:physiology*; D010455:Peptides / Q000235:genetics / Q000502:physiology; D014176:Protein Biosynthesis; D017510:Protein Folding; D011994:Recombinant Proteins / Q000235:genetics
D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D010455:Peptides; D011994:Recombinant Proteins; D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu