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Transfer RNA Synthesis

Transfer RNA Synthesis

One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...

Transfer RNA Synthesis

Transfer RNA Synthesis

One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...

tRNA Activation

tRNA Activation

Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...

tRNA Activation

tRNA Activation

Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...

RNA Editing

RNA Editing

RNA editing is a post-transcriptional modification where a precursor mRNA (pre-mRNA) nucleotide sequence is changed by base insertion, deletion, or modification. The extent of RNA editing varies from a few hundred bases, in mitochondrial DNA of trypanosomes, to a just single base, in nuclear genes of mammals. Even a single base change in the pre-mRNA can convert a codon for one amino acid into the codon for another amino acid or a stop codon. This type of re-coding can significantly affect the...

Pre-mRNA Processing: Modification of pre-mRNA Ends

Pre-mRNA Processing: Modification of pre-mRNA Ends

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a cap to the 5' end of the growing transcript. In this process, a 5' phosphate is replaced by modified guanosine that has a methyl group attached (7-methyl guanosine). This 5' cap helps the cell...

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Related Experiment Video

Updated: Jul 3, 2026

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

Published on: October 8, 2018

Amino acid modifications on tRNA.

Jing Yuan¹, Kelly Sheppard, Dieter Söll

¹Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.

Acta Biochimica Et Biophysica Sinica

|July 8, 2008

Summary

Accurate protein synthesis relies on specific aminoacyl-tRNAs (aa-tRNAs). Indirect pathways create aa-tRNAs for Gln, Asn, Cys, and Sec, involving tRNA-dependent modifying enzymes.

Area of Science:

Molecular Biology
Biochemistry
Evolutionary Biology

Background:

Accurate translation requires cognate aminoacyl-tRNAs (aa-tRNAs).
Most amino acids are directly charged by aminoacyl-tRNA synthetases.
Four amino acids (Gln, Asn, Cys, Sec) utilize indirect aa-tRNA formation pathways.

Purpose of the Study:

To investigate the indirect pathways of aminoacyl-tRNA formation.
To understand the role of tRNA-dependent modifying enzymes in ensuring translation fidelity.
To explore the evolutionary significance of these indirect pathways across life domains.

Main Methods:

Analysis of tRNA charging mechanisms.
Identification and characterization of tRNA-dependent modifying enzymes.

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Characterizing RNA Modifications in Single Neurons Using Mass Spectrometry

Characterizing RNA Modifications in Single Neurons Using Mass Spectrometry

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Genome-wide Analysis of Aminoacylation (Charging) Levels of tRNA Using Microarrays

Genome-wide Analysis of Aminoacylation (Charging) Levels of tRNA Using Microarrays

Published on: June 18, 2010

Related Experiment Videos

Last Updated: Jul 3, 2026

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

Published on: October 8, 2018

Characterizing RNA Modifications in Single Neurons Using Mass Spectrometry

Characterizing RNA Modifications in Single Neurons Using Mass Spectrometry

Published on: April 21, 2022

Genome-wide Analysis of Aminoacylation (Charging) Levels of tRNA Using Microarrays

Genome-wide Analysis of Aminoacylation (Charging) Levels of tRNA Using Microarrays

Published on: June 18, 2010

Comparative genomics to trace evolutionary spread.

Main Results:

Indirect pathways involve initial charging of noncognate amino acids or tRNAs.
TRNA-dependent enzymes transform amino acids on tRNAs to cognate forms.
These pathways are conserved across bacteria, archaea, and eukaryotes.

Conclusions:

Indirect aa-tRNA formation is a crucial mechanism for translation fidelity for specific amino acids.
TRNA-dependent modifying enzymes are key players in these essential pathways.
The widespread distribution suggests an ancient origin and evolutionary importance.