Related Experiment Video
Updated: Jun 19, 2026

Mitochondrial Transformation in Baker's Yeast to Study Translation and Respiratory Complex Assembly
Published on: June 7, 2024
Biogenesis of glutaminyl-mt tRNAGln in human mitochondria
Asuteka Nagao1, Takeo Suzuki, Takayuki Katoh
1Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Building 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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.
Related Concept Videos
Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Energy to Drive Translocation
Generally, polypeptides are unfolded by two distinct...
Protein Transport into the Inner Mitochondrial Membrane
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Animal Mitochondrial Genetics
Mitochondrial Precursor Proteins
Most of the mitochondrial precursors...

