| Type: | Family | Name: | Tyrosine-tRNA ligase, archaeal/eukaryotic-type |
| Description: | Tyrosine-tRNA ligases (also known as Tyrosyl-tRNA synthetases) () are widely distributed, being found in archaea, bacteria and eukaryotes. Studies on tyrosine-tRNA ligase have shown that the 'KMSKS' motif plays a role in the initial binding of tRNA(Tyr) to tyrosine-tRNA ligase [].The aminoacyl-tRNA synthetase (also known as aminoacyl-tRNA ligase) catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction. These proteins differ widely in size and oligomeric state, and have limited sequence homology []. The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossman fold catalytic domain and are mostly monomeric []. Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices [], and are mostly dimeric or multimeric, containing at least three conserved regions [, , ]. However, tRNA binding involves an alpha-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan and valine belong to class I synthetases. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases. Based on their mode of binding to the tRNA acceptor stem, both classes of tRNA synthetases have been subdivided into three subclasses, designated 1a, 1b, 1c and 2a, 2b, 2c.Two groups can be distinguished among tyrosyl-tRNA synthetases. One group contains bacterial and organellar eukaryotic examples. The other contains archaeal and cytosolic eukaryotic examples. This entry represents the archaeal and cytosolic eukaryotic tyrosyl-tRNA synthetases. | Short Name: | Tyr-tRNA-ligase_arc/euk-type |
