Family

Glycine-tRNA ligase, alpha subunit (IPR002310)

Short name: Gly-tRNA_ligase_asu

Family relationships

Description

This entry represents the alpha subunit of glycine-tRNA ligase (also known as glycyl-tRNA synthetase alpha subunit). It is responsible for the attachment of glycine to the 3' OH group of ribose of the appropriate tRNA. This domain is primarily responsible for the ATP-dependent formation of the enzyme bound aminoacyl-adenylate.

In eubacteria, glycine-tRNA ligase (EC:6.1.1.14) is an alpha2/beta2 tetramer composed of 2 different subunits [PMID: 6309809, PMID: 7962006, PMID: 7665503]. In some eubacteria, in archaea and eukaryota, glycine-tRNA ligase is an alpha2 dimer (see IPR002315). It belongs to class IIc and is one of the most complex ligases. What is most interesting is the lack of similarity between the two types: divergence at the sequence level is so great that it is impossible to infer descent from common genes. The alpha and beta subunits also lack significant sequence similarity. However, they are translated from a single mRNA [PMID: 6309809], and a single chain glycine-tRNA ligase from Chlamydia trachomatis has been found to have significant similarity with both domains, suggesting divergence from a single polypeptide chain [PMID: 7665503].

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 [PMID: 10704480,PMID: 12458790]. 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 [PMID: 10447505].

GO terms

Biological Process

GO:0006426 glycyl-tRNA aminoacylation

Molecular Function

GO:0005524 ATP binding
GO:0004820 glycine-tRNA ligase activity
GO:0000166 nucleotide binding

Cellular Component

GO:0005737 cytoplasm

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
HAMAP
Pfam
TIGRFAMs
PRINTS
CDD