The tRNA glycylation system is amongst the most complex aminoacylation systems since neither the oligomeric structure of the enzymes nor the discriminator base in tRNAs are conserved in the phylae. To understand better this structural diversity and its functional consequences, the prokaryotic glycylation system from @entity4691 , an extreme thermophile, was investigated and its structural and functional inter-relations with those of other origins analyzed. Alignments of the protein sequence of the dimeric thermophilic glycyl-tRNA synthetase ( @entity4022 -tRNA synthetase) derived from its gene with sequences of other dimeric @entity4022 -tRNA synthetases revealed an atypical character of motif 1 in all these class 2 synthetases. Interestingly, the sequence of the prokaryotic thermophilic enzyme resembles eukaryotic and archaebacterial @entity4022 -tRNA synthetases, which are all dimeric, and diverges drastically from the tetrameric enzymes from other prokaryotes. Cross aminoacylations with tRNAs and synthetases of different origins provided information about functional interrelations between the glycylation systems. Efficient glycylations involving partners from @entity4691 and @entity526 showed conservation of the recognition process in prokaryotes despite strong structural variations of the synthetases. However, @entity4022 -tRNA synthetase from @entity4691 acylates eukaryotic tRNA( @entity4022 ) while the charging ability of the @entity526 enzyme is restricted to prokaryotic tRNA( @entity4022 ). A similar behaviour is found in eukaryotic systems where the restricted species specificity for tRNA glycylation of @entity1 @entity4022 -tRNA synthetase contrasts with the relaxed specificity of the @entity375 enzyme. The consensus sequence of the tRNAs charged by the various @entity4022 -tRNA synthetases reveals conservation of only G1-C72 in the acceptor arm, C35 and C36 in the anticodon, and the (G10-Y25)-G45 triplet involved in tRNA folding. Conservation of these nucleotides indicates their key role in glycylation and suggests that they were part of the ancestral @entity2228 identity set. These features are discussed in the context of the phylogenic connections between prokaryotes, eukaryotes, and archaebacteria, and of the particular place of @entity4691 in this phylogeny.

Glycyl-tRNA synthetase from XXXX --wide structural divergence with other prokaryotic glycyl-tRNA synthetases and functional inter-relation with prokaryotic and eukaryotic glycylation systems.

@entity1 :: ('9606', 'Species') :: ['mammalian'] @entity4691 :: ('274', 'Species') :: ['T. thermophilus', 'Thermus thermophilus'] @entity2228 :: ('CHEBI:57305', 'Chemical') :: ['glycine'] @entity4022 :: ('MESH:C066286', 'Chemical') :: ['Gly'] @entity375 :: ('4932', 'Species') :: ['yeast'] @entity526 :: ('562', 'Species') :: ['Escherichia coli', 'E. coli']
@entity4691 :: (274,Species) :: ['Thermus thermophilus']
