Aminoacyl tRNA synthetases, class I

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Glutamyl/glutaminyl-tRNA synthetase, class Ic

The aminoacyl-tRNA synthetases (EC 6.1.1.) 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.[1] 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.[2] Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices,[3] and are mostly dimeric or multimeric, containing at least three conserved regions.[4][5][6] 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; these synthetases are further divided into three subclasses, a, b and c, according to sequence homology. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases.[7]

Glutamyl-tRNA synthetase (EC is a class Ic synthetase and shows several similarities with glutaminyl-tRNA synthetase concerning structure and catalytic properties. It is an alpha2 dimer. To date one crystal structure of a glutamyl-tRNA synthetase (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 synthetases and resembles the corresponding part of E. coli GlnRS, whereas the C-terminal half exhibits a GluRS-specific structure.[8]

Human proteins containing this domain[edit]



  1. ^ Delarue M, Moras D, Poch O, Eriani G, Gangloff J (1990). "Partition of tRNA synthetases into two classes based on mutually exclusive sets of sequence motifs". Nature. 347 (6289): 203–206. doi:10.1038/347203a0. PMID 2203971.
  2. ^ Moras D, Konno M, Shimada A, Nureki O, Tateno M, Yokoyama S, Sugiura I, Ugaji-Yoshikawa Y, Kuwabara S, Lorber B, Giege R (2000). "The 2.0 A crystal structure of Thermus thermophilus methionyl-tRNA synthetase reveals two RNA-binding modules". Structure. 8 (2): 197–208. doi:10.1016/S0969-2126(00)00095-2. PMID 10673435.
  3. ^ Perona JJ, Steitz TA, Rould MA (1993). "Structural basis for transfer RNA aminoacylation by Escherichia coli glutaminyl-tRNA synthetase". Biochemistry. 32 (34): 8758–8771. doi:10.1021/bi00085a006. PMID 8364025.
  4. ^ Delarue M, Moras D (1993). "The aminoacyl-tRNA synthetase family: modules at work". BioEssays. 15 (10): 675–687. doi:10.1002/bies.950151007. PMID 8274143.
  5. ^ Schimmel P (1991). "Classes of aminoacyl-tRNA synthetases and the establishment of the genetic code". Trends Biochem. Sci. 16 (1): 1–3. doi:10.1016/0968-0004(91)90002-D. PMID 2053131.
  6. ^ Cusack S, Leberman R, Hartlein M (1991). "Sequence, structural and evolutionary relationships between class 2 aminoacyl-tRNA synthetases". Nucleic Acids Res. 19 (13): 3489–3498. doi:10.1093/nar/19.13.3489. PMC 328370. PMID 1852601.
  7. ^ Bairoch A (2004). "List of aminoacyl-tRNA synthetases": –.
  8. ^ Soll D, Freist W, Gauss DH, Lapointe J (1997). "Glutamyl-tRNA sythetase". Biol. Chem. 378 (11): 1313–1329. doi:10.1515/bchm.1997.378.11.1299. PMID 9426192.
This article incorporates text from the public domain Pfam and InterPro: IPR000924