Family

Isoleucine-tRNA ligase, type 1 (IPR023585)

Short name: Ile-tRNA-ligase_type1

Family relationships

Description

Isoleucine-tRNA ligase (also known as Isoleucyl-tRNA synthetase)(EC:6.1.1.5) is an alpha monomer that belongs to class Ia. The enzyme, isoleucine-tRNA ligase, activates not only the cognate substrate L-isoleucine but also the minimally distinct L-valine in the first, aminoacylation step. Then, in a second, "editing" step, the ligase itself rapidly hydrolyses only the valylated products [PMID: 9554847, PMID: 10446055] as shown from the crystal structures.

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].

In eukaryotes, two forms of isoleucine-tRNA synthetase exist, a cytoplasmic form and a mitochondrial form [PMID: 7607232]. Type 1 includes bacterial and mitochondrial (gene iars2) isoleucine-tRNA ligases.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004822 isoleucine-tRNA ligase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

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