The Trna plays the role of an adapter between the codons and the amino acids they specify. And Rrna in addition to its structural role of ribosomes in association with proteins, it has a role in the attachment of the Mrna (ARNr16S in prokaryotes) and the formation of bonds peptide (activity peptidyl transferase of the 23S Rrna in prokaryotes). The binding of the tRNA with its specific amino acid is catalyzed by an enzyme: aminoacyl tRNA synthetase.

Figure 15: Structure of the Trna discharged (without amino acid). This structure in the so-called clover-leaf. The amino acid is fixed at the level of the ribosome from the A terminal of the end acceptor.

Figure 16 : Response of aminoacylation catlysée by an aminoacyl-Trna synthetase.