Functional characterization of eukaryotic Thg1 enzymes
| Autor: | TRAN HANH PHUOC, 陳幸福 |
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| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 Aminoacyl-tRNA synthetases (aaRSs) are essential translation enzymes, each catalyzes the coupling of a specific amino acid to its cognate tRNAs. The presence of an additional 5’ guanosine residue (G-1) is a unique feature of tRNAHis in all three domains of life. This unusual G-1 residue is the major identity element of tRNAHis and is essential for recognition by histidyl-tRNA synthetase (HisRS). The functional significance of G-1 is evidenced by the existence of two entirely distinct mechanisms: G-1 is encoded in the tRNAHis gene of bacteria (and many archaea) and G-1 is added post-transcriptionally by tRNAHis guanylyltransferase (Thg1) in eukaryotes. Thg1 possesses an efficient 3’–5’polymerase activity that specifically adds the G-1 residue by recognizing the anticodon of tRNAHis. Typically, G-1 addition to tRNAHis with A73 is mediated via an ATP-dependent mechanism in eukaryotes, while G-1 addition to tRNAHis with C73 is mediated via a GTP-dependent mechanism in prokaryotes. We reported herein that like human Thg1, Thg1 homologs of Drosophila melanogaster and Bombyx mori also possess a mitochondrial targeting signal (MTS). As a result, these Thg1 enzymes can be targeted to both cytoplasm and mitochondria. Moreover, we found that these Thg1 enzymes can attach G-1 to both cytoplasmic tRNAsHis with A73 and mitochondrial tRNAsHis with C73. Interestingly, Drosophila Thg1 enzyme attaches G-1 to tRNAnHis via an ATP-dependent mechanism, while it attaches G-1 to tRNAmHis via a GTP-dependent mechanism. This study provides new insight into the mechanisms of tRNAHis maturation in the cytoplasm and mitochondria. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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