aminoacyltRNA

An aminoacyl-tRNA, commonly referred to as a charged tRNA, is a transfer RNA molecule that has been covalently linked to a specific amino acid. This charged form is the substrate that delivers the amino acid to the ribosome during translation, where codon–anticodon pairing between mRNA and tRNA determines which amino acid is added to the growing polypeptide chain.

Charging is carried out by aminoacyl-tRNA synthetases, a family of enzymes that recognize both a particular amino acid and its corresponding tRNA. In the charging reaction, the amino acid is first activated with ATP to form aminoacyl-AMP, which is then transferred to the 3' end of the tRNA, producing aminoacyl-tRNA and releasing AMP and pyrophosphate. Many synthetases contain proofreading or editing activities to prevent mischarging, either by hydrolyzing misactivated amino acids or by detaching incorrectly attached amino acids from tRNA.

In translation, aminoacyl-tRNAs are delivered to the ribosome by elongation factors (such as EF-Tu in bacteria or EF1A in eukaryotes). The correct codon on the mRNA pairs with the tRNA anticodon, enabling the ribosome to catalyze peptide bond formation. Organisms possess multiple isoacceptor tRNAs that carry the same amino acid but have different anticodons, broadening codon recognition. The term aminoacyl-tRNA distinguishes the charged state from deacylated tRNA; the latter can become charged again, or participate in other RNA processes if not engaged in translation.