Functional compatibility of elongation factors between mammalian mitochondrial and bacterial ribosomes: characterization of GTPase activity and translation elongation by hybrid ribosomes bearing heterologous L7/12 proteins.
The mammalian mitochondrial (mt) ribosome (mitoribosome) is a bacterial-type ribosome but has a highly protein-rich composition. Almost half of the rRNA contained in the bacterial ribosome is replaced with proteins in the mitoribosome. Escherichia coli elongation factor G (EF-G Ec) has no translocase activity on the mitoribosome but EF-G mt is functional on the E.coli ribosome. To investigate the functional equivalency of the mt and E.coli ribosomes, we prepared hybrid mt and E.coli ribosomes. The hybrid mitoribosome containing E.coli L7/12 (L7/12 Ec) instead of L7/12 mt clearly activated the GTPase of EF-G Ec and efficiently promoted its translocase activity in an in vitro translation system. Thus, the mitoribosome is functionally equivalent to the E.coli ribosome despite their distinct compositions. The mt EF-Tu-dependent translation activity of the E.coli ribosome was also clearly enhanced by replacing the C-terminal domain (CTD) of L7/12 Ec with the mt counterpart (the hybrid E.coli ribosome). This strongly indicates that the CTD of L7/12 is responsible for EF-Tu function. These results demonstrate that functional compatibility between elongation factors and the L7/12 protein in the ribosome governs its translational specificity.
Terasaki
Maki
M
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bldg. FSB-301, 5-1-5 Kashiwanoha, Kashiwa, 277-8562, Chiba Prefecture, Japan.
Suzuki
Tsutomu
T
Hanada
Takao
T
Watanabe
Kimitsuna
K
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008322:Mammals; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010441:Peptide Chain Elongation, Translational; D020653:Peptide Elongation Factor G / Q000378:metabolism*; D010444:Peptide Elongation Factor Tu / Q000378:metabolism*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism*
D029968:Escherichia coli Proteins; D024101:Mitochondrial Proteins; D020653:Peptide Elongation Factor G; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C016700:ribosomal protein L7-L12; D010444:Peptide Elongation Factor Tu