Читать книгу Algorithms in Bioinformatics - Paul A. Gagniuc - Страница 23

On the other side of the translation, an ancient group of enzymes set the rules of the genetic code [57]. The aminoacyl–tRNA synthetase (tRNA-ligase) represents a group of enzymes. The function of these enzymes is to attach an appropriate amino acid to a corresponding tRNA (Figure 1.3.c). Many of these enzymes recognize their tRNA molecules using the anticodon [58]. Consequently, there is one tRNA-ligase for each tRNA–amino acid pair. For instance, in humans there are twenty different types of aminoacyl–tRNA synthetases, one for each amino acid of the genetic code [59]. Some organisms lack the genes needed for all twenty aminoacyl–tRNA synthetases. However, such organisms use all twenty amino acids for protein synthesis. In such cases, a tradeoff is made in the complexity of a tRNA-ligase, such that one enzyme associates more than one pair [60, 61]. Thus, the tRNA matching with an amino acid is based on additional properties exhibited by the tRNA, such as the geometry (shape) of the molecule, specific nucleotide positions along the tRNA chain, and so on [62].