Glutamyl/glutaminyl-tRNA synthetase, class Ib, catalytic domain (IPR020058)

Short name: Glu/Gln-tRNA-synth_Ib_cat-dom

Domain relationships



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 [PMID: 2203971]. 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 [PMID: 10673435]. Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices [PMID: 8364025], and are mostly dimeric or multimeric, containing at least three conserved regions [PMID: 8274143, PMID: 2053131, PMID: 1852601]. 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.

Glutamate-tRNA ligase (also known as glutamyl-tRNA synthetase)(EC: is a class Ic ligase and shows several similarities with glutamate-tRNA ligase concerning structure and catalytic properties. It is an alpha2 dimer. To date one crystal structure of a glutamate-tRNA ligase (Thermus thermophilus) has been solved. The molecule has the form of a bent cylinder and consists of four domains. The N-terminal half (domains 1 and 2) contains the 'Rossman fold' typical for class I ligases and resembles the corresponding part of Escherichia coli GlnRS, whereas the C-terminal half exhibits a GluRS-specific structure [PMID: 9426192].

GO terms

Biological Process

GO:0043039 tRNA aminoacylation

Molecular Function

GO:0005524 ATP binding
GO:0016876 ligase activity, forming aminoacyl-tRNA and related compounds

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.