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[Biochemistry](https://durgical.com/en/biochemistry/) · Topic

# Transfer RNA (tRNA)

tRNA is the adaptor of translation: it carries an amino acid at one end and, at the other, an anticodon that reads the mRNA codon.

Updated 2026-11-01

## Key facts

- About 75–90 nucleotides; a cloverleaf in 2D and an 'L' shape in 3D.
- 3' CCA end: the amino acid attaches there (ester bond). The anticodon sits in the opposite loop.
- Transcribed by RNA polymerase III, with many modified bases (pseudouridine, dihydrouridine, inosine).
- Each aminoacyl-tRNA synthetase loads its amino acid onto the right tRNA using ATP and corrects mistakes (editing).
- Wobble at the 1st anticodon base lets one tRNA read several codons.

## In detail

- Arms: acceptor (CCA), D (dihydrouridine), anticodon, variable and TΨC (binds the ribosome).
- The anticodon pairs antiparallel with the codon: anticodon 5'-CAU-3' reads codon 5'-AUG-3'.
- Inosine at the wobble position can pair with U, C or A.
- The initiator tRNA differs from the one carrying methionine inside the protein; in bacteria it carries formyl-methionine.
- Mitochondria have their own 22 tRNAs encoded by mitochondrial DNA.

**Also called**
tRNA

## Clinical notes

- Mutations in the mitochondrial leucine tRNA (MT-TL1, mostly m.3243A>G) cause MELAS; in the lysine tRNA (MT-TK), MERRF.
- Mupirocin, a topical antibiotic, inhibits bacterial isoleucyl-tRNA synthetase.

## Related conditions

- [MELAS (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes)](https://durgical.com/en/conditions/melas/)

## Related

- [Translation and the genetic code](https://durgical.com/en/biochemistry/topics/translation-and-the-genetic-code/)
- [Ribosome (and the antibiotics that target it)](https://durgical.com/en/biochemistry/enzymes/ribosome/)
- [RNA polymerases I, II and III](https://durgical.com/en/biochemistry/enzymes/rna-polymerases-i-ii-and-iii/)
- [RNA processing (cap, poly-A tail and splicing)](https://durgical.com/en/biochemistry/topics/rna-processing/)

## Test yourself

Think of the answer, then tap the question to see it.

## At which end of the tRNA does the amino acid attach?

At the 3' end, to the adenosine of the CCA sequence, by an ester bond.

## Which enzyme makes sure each tRNA carries the right amino acid?

The specific aminoacyl-tRNA synthetase, which also checks and corrects mistakes.

## What does wobble allow?

The first anticodon base pairs loosely with the third codon base, so one tRNA can read several codons.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Transfer RNA (tRNA)](https://www.genome.gov/genetics-glossary/Transfer-RNA-tRNA) (National Human Genome Research Institute (NHGRI), 2026); [tRNA Aminoacylation](https://reactome.org/PathwayBrowser/#/R-HSA-379724) (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

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Representative model, for educational purposes only.

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