| Literature DB >> 19805282 |
Asuteka Nagao1, Takeo Suzuki, Takayuki Katoh, Yuriko Sakaguchi, Tsutomu Suzuki.
Abstract
Mammalian mitochondrial (mt) tRNAs, which are required for mitochondrial protein synthesis, are all encoded in the mitochondrial genome, while mt aminoacyl-tRNA synthetases (aaRSs) are encoded in the nuclear genome. However, no mitochondrial homolog of glutaminyl-tRNA synthetase (GlnRS) has been identified in mammalian genomes, implying that Gln-tRNA(Gln) is synthesized via an indirect pathway in the mammalian mitochondria. We demonstrate here that human mt glutamyl-tRNA synthetase (mtGluRS) efficiently misaminoacylates mt tRNA(Gln) to form Glu-tRNA(Gln). In addition, we have identified a human homolog of the Glu-tRNA(Gln) amidotransferase, the hGatCAB heterotrimer. When any of the hGatCAB subunits were inactivated by siRNA-mediated knock down in human cells, the Glu-charged form of tRNA(Gln) accumulated and defects in respiration could be observed. We successfully reconstituted in vitro Gln-tRNA(Gln) formation catalyzed by the recombinant mtGluRS and hGatCAB. The misaminoacylated form of tRNA(Gln) has a weak binding affinity to the mt elongation factor Tu (mtEF-Tu), indicating that the misaminoacylated form of tRNA(Gln) is rejected from the translational apparatus to maintain the accuracy of mitochondrial protein synthesis.Entities:
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Year: 2009 PMID： 19805282 PMCID： PMC2752530 DOI： 10.1073/pnas.0907602106
Source DB: PubMed Journal: Proc Natl Acad Sci U S A ISSN： 0027-8424 Impact factor: 11.205