Proline-tRNA ligase, class IIa, archaeal-type (IPR004499)

Short name: Pro-tRNA-ligase_IIa_arc-type

Overlapping homologous superfamilies


Family relationships


Proline-tRNA ligase (also known as Prolyl-tRNA synthetase) is a class II tRNA ligase and is recognised by IPR002314, which recognises tRNA ligases for Gly, His, Ser, and Pro. The proline-tRNA ligases are divided into two widely divergent families. This family includes the archaeal enzyme, the Pro-specific domain of a human multifunctional tRNA ligase, and the enzyme from the spirochete Borrelia burgdorferi (Lyme desease spirochete). The other family, IPR004500, includes enzymes from Escherichia coli, Bacillus subtilis, Synechocystis sp. (strain PCC 6308), and one of the two proline-tRNA ligases of Saccharomyces cerevisiae (Baker's yeast).

The aminoacyl-tRNA synthetases (also known as aminoacyl-tRNA ligases) 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, valine, and some lysine synthetases (non-eukaryotic group) belong to class I synthetases. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, phenylalanine, proline, serine, threonine, and some lysine synthetases (non-archaeal group), 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:0006433 prolyl-tRNA aminoacylation

Molecular Function

GO:0005524 ATP binding
GO:0004827 proline-tRNA ligase activity

Cellular Component

GO:0005737 cytoplasm

Contributing signatures

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