PROSITE documentation PDOC00161
Aminoacyl-transfer RNA synthetases class-I signature


Aminoacyl-tRNA synthetases (EC 6.1.1.-) [1] are a group of enzymes which activate amino acids and transfer them to specific tRNA molecules as the first step in protein biosynthesis. In prokaryotic organisms there are at least twenty different types of aminoacyl-tRNA synthetases, one for each different amino acid. In eukaryotes there are generally two aminoacyl-tRNA synthetases for each different amino acid: one cytosolic form and a mitochondrial form. While all these enzymes have a common function, they are widely diverse in terms of subunit size and of quaternary structure.

A few years ago it was found [2] that several aminoacyl-tRNA synthetases share a region of similarity in their N-terminal section, in particular the consensus tetrapeptide His-Ile-Gly-His ('HIGH') is very well conserved. The 'HIGH' region has been shown [3] to be part of the adenylate binding site. The 'HIGH' signature has been found in the aminoacyl-tRNA synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan, and valine. These aminoacyl-tRNA synthetases are referred to as class-I synthetases [4,5,6] and seem to share the same tertiary structure based on a Rossmann fold.


In position 8 of the pattern His is present in all tRNA-synthetases of class-I except in some bacterial tryptophanyl-tRNA synthetases which have a Thr in that position.

Last update:

November 1997 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

AA_TRNA_LIGASE_I, PS00178; Aminoacyl-transfer RNA synthetases class-I signature  (PATTERN)


1AuthorsSchimmel P.
TitleAminoacyl tRNA synthetases: general scheme of structure-function relationships in the polypeptides and recognition of transfer RNAs.
SourceAnnu. Rev. Biochem. 56:125-158(1987).
PubMed ID3304131

2AuthorsWebster T. Tsai H. Kula M. Mackie G.A. Schimmel P.
TitleSpecific sequence homology and three-dimensional structure of an aminoacyl transfer RNA synthetase.
SourceScience 226:1315-1317(1984).
PubMed ID6390679

3AuthorsBrick P. Bhat T.N. Blow D.M.
TitleStructure of tyrosyl-tRNA synthetase refined at 2.3 A resolution. Interaction of the enzyme with the tyrosyl adenylate intermediate.
SourceJ. Mol. Biol. 208:83-98(1989).
PubMed ID2504923

4AuthorsDelarue M. Moras D.
TitleThe aminoacyl-tRNA synthetase family: modules at work.
SourceBioEssays 15:675-687(1993).
PubMed ID8274143

5AuthorsSchimmel P.
TitleClasses of aminoacyl-tRNA synthetases and the establishment of the genetic code.
SourceTrends Biochem. Sci. 16:1-3(1991).
PubMed ID2053131

6AuthorsNagel G.M. Doolittle R.F.
TitleEvolution and relatedness in two aminoacyl-tRNA synthetase families.
SourceProc. Natl. Acad. Sci. U.S.A. 88:8121-8125(1991).
PubMed ID1896459

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