| Type: | Domain | Name: | Aminoacyl-tRNA synthetase, class I, anticodon-binding domain, subdomain 2 |
| Description: | 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.Structurally, an alpha-helix-bundle anticodon-binding domain characterises the class Ia synthetases, whereas the class Ib synthetases, GlnRS and GluRS have distinct anticodon-binding domains. The anticodon-binding domain has a multi-helical structure, consisting of two all-alpha subdomains. The Rossmann-fold and anticodon-binding domains are connected by a beta-alpha-alpha-beta-alpha topology ('SC fold') domain that contains the class I specific KMSKS motif []. | Short Name: | aa-tRNA-synth_I_codon-bd_sub2 |
