Disease relevance of ECs0710

• The amino-terminal half of GluRS shows a geometrical similarity with that of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) of the same subclass in class I, comprising the class I-specific Rossmann fold domain and the intervening subclass-specific alpha/beta domain [1].
• The enzyme furnishes a means for formation of correctly charged Gln-tRNAGln through the transamidation of misacylated Glu-tRNAGln, functionally replacing the lack of glutaminyl-tRNA synthetase activity in Gram-positive eubacteria, cyanobacteria, Archaea, and organelles [2].
• The glutaminyl-tRNA synthetase (GlnRS) from the radiation-resistant bacterium Deinococcus radiodurans differs from known GlnRSs and other tRNA synthetases by the presence of an additional C-terminal domain resembling the C-terminal region of the GatB subunit of tRNA-dependent amidotransferase (AdT) [3].

High impact information on ECs0710

• In striking contrast to the beta-barrel structure of the GlnRS carboxyl-terminal half, the GluRS carboxyl-terminal half displayed an all-alpha-helix architecture, an alpha-helix cage, and mutagenesis analyses indicated that it had a role in the anticodon recognition [1].
• All three mischarging mutant enzymes still retain a certain degree of tRNA specificity; in vivo they acylate supE glutaminyl tRNA (tRNA(Gln] and supF tRNA(Tyr) but not a number of other suppressor tRNA's. These genetic experiments define two positions in GlnRS where amino acid substitution results in a relaxed specificity of tRNA discrimination [4].
• An investigation of the role of tRNA in the catalysis of aminoacylation of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) has revealed that the accuracy of specific interactions between GlnRS and tRNAGln determines amino acid affinity [5].
• Mutations in GlnRS at D235, which makes contacts with nucleotides in the acceptor stem of tRNAGln, and at R260 in the enzyme's active site were found to be independent during tRNA binding but interactive for aminoacylation [5].
• The catalytic core of GlnRS, which is structurally conserved in other class I synthetases, is therefore sufficient for the aminoacylation of tRNA substrates [6].

Chemical compound and disease context of ECs0710

• As an approach to inducible suppression of nonsense mutations in mammalian cells, we described recently an amber suppression system in mammalian cells dependent on coexpression of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) along with the E. coli glutamine-inserting amber suppressor tRNA [7].
• The E. coli GlnRS coding sequence attached to a minimal mammalian cell promoter was placed downstream of seven tandem tetracycline operator sequences [7].
• The urea induced equilibrium denaturation behavior of glutaminyl-tRNA synthetase from Escherichia coli (GlnRS) in 0.25 m potassium l-glutamate, a naturally occurring osmolyte in E. coli, has been studied [8].
• Structure-based mutational analysis was employed to probe an unusual intramolecular interaction between partially buried glutamate residues adjacent to the active site of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) [9].

Biological context of ECs0710

• Correct aminoacylation depends on the set of nucleotides (identity elements) in tRNA(Gln) responsible for correct interaction with GlnRS [10].
• Our results indicate that the catalytic and substrate recognition properties are carried by distinct domains of GlnRS, and support the notion that class I aminoacyl-tRNA synthetases evolved from a common ancestor, jointly with tRNAs and the genetic code, by the addition of non-catalytic domains conferring new recognition specificities [6].
• Steady-state kinetics revealed that interactions between tRNA identity nucleotides and their recognition sites in the enzyme modulate the amino acid affinity of GlnRS [11].
• Plasmids carrying the E. coli GlnRS gene can be stably maintained in yeast [12].
• Phylogenetic analyses predict that GlnRS arose from glutamyl-tRNA synthetase (GluRS), via gene duplication with subsequent evolution of specificity [13].

Anatomical context of ECs0710

• GlnRS is absent, however, in archaea, and most bacteria, organelles, and chloroplasts [13].
• The tetracycline transactivator-mediated expression of E. coli GlnRS was essentially completely blocked in HeLa or COS-1 cells grown in the presence of tetracycline [7].

Associations of ECs0710 with chemical compounds

• Crystal structures of the GlnRS x tRNA complex bound to either amino acid have previously shown that glutamine and glutamate bind in distinct positions in the active site, providing a structural basis for the amino acid-dependent modulation of tRNA affinity [14].
• Further transient kinetics experiments showed that tRNA(Gln) binds to GlnRS approximately 60-fold weaker when noncognate glutamate is present and that glutamate reduces the association rate of tRNA with the enzyme by 100-fold [14].
• Two different fluorescent probes, pyrenylmaleimide and acrylodan, were used to specifically label a nonessential sulfhydryl group of GlnRS [15].
• 5,5'-Bis(8-anilino-1-naphthalene sulfonate) (bis-ANS), a non-covalent fluorescent probe, was also used to probe for conformational changes in GlnRS [16].
• The GlnRS molecule consists of four domains, the catalytic site is located in the Rossman fold, typical for class I synthetases, and the reaction mechanism follows the normal adenylate pathway [17].

Other interactions of ECs0710

• A pertinent question to ask is whether, in the advent of GlnRS, a transient GluRS-like intermediate could have been retained in an extant organism [13].
• The superimposable dinucleotide fold domains of MetRS, GlnRS and TyrRS define structurally equivalent amino acids which have been used to constrain the sequence alignments of the 10 class I aminoacyl-tRNA synthetases (aaRS) [18].

Analytical, diagnostic and therapeutic context of ECs0710

• Repeated rounds of DNA shuffling and oligonucleotide-directed mutagenesis followed by genetic selection resulted in mutant GlnRS enzymes that efficiently acylate the engineered tRNA with glutamine in vitro [19].

References