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Studies on transfer RNA from mycobacteria
Abstract:
Active preparations of tRNA and aminoacyl-tRNA synthetases have been isolated from exponentially growing cells of Mycobacterium smegmatis and Mycobacterium tuberculosis H37Rv. Though the aminoacyl-tRNA synthetases of older cells retain their activity, the tRNAs seem to undergo modification and show poorer activity. The mycobacterial enzyme preparations catalyse homologous and heterologous aminoacylation between tRNA from the two species (M. smegmatis and M. tuberculosis H37Rv) or from Escherichia coli, with equal efficiency; tRNA samples from eukaryotic cells (yeast and rat liver) do not serve as substrates for the mycobacterial synthetases. The analytical separation of the different amino acid specific tRNAs from M. smegmatis resembles the pattern found in other bacteria. Purification of valine- (three species) and methionine-specific tRNA (two species) to 70-80% purity has been accomplished by using column-chromatographic techniques. Of the two species of tRNAMet, one can be formylated in the presence of formyl tetrahydrofolate and the transformylase from mycobacteria.
Insights
Mycobacterium tRNA and aminoacyl-tRNA synthetases are active in younger cells but less so in older cells. These enzymes efficiently aminoacylate bacterial tRNA but not eukaryotic tRNA.
Area of Science:
- Molecular Biology
- Biochemistry
- Microbiology
Background:
- Transfer RNA (tRNA) and aminoacyl-tRNA synthetases are crucial for protein synthesis.
- Investigating these components in mycobacteria is important for understanding their unique biology.
Purpose of the Study:
- To isolate and characterize active tRNA and aminoacyl-tRNA synthetases from Mycobacterium smegmatis and Mycobacterium tuberculosis.
- To assess the substrate specificity and activity of these enzymes.
Main Methods:
- Isolation of tRNA and aminoacyl-tRNA synthetases from exponentially growing and older mycobacterial cells.
- Enzyme assays for aminoacylation using homologous and heterologous tRNAs.
- Column chromatography for tRNA purification.
Main Results:
- Active tRNA and aminoacyl-tRNA synthetases were isolated from M. smegmatis and M. tuberculosis.
- Enzyme activity was retained in older cells, but tRNA showed reduced activity.
- Mycobacterial synthetases efficiently aminoacylated bacterial tRNA (M. smegmatis, M. tuberculosis, E. coli) but not eukaryotic tRNA (yeast, rat liver).
- Specific tRNAs (valine, methionine) were purified, and one tRNAMet species was formylated.
Conclusions:
- Mycobacterial aminoacyl-tRNA synthetases exhibit broad specificity for bacterial tRNAs.
- Age-related modifications affect tRNA activity in mycobacteria.
- These findings provide insights into mycobacterial translation machinery.