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Gene Review:

gltX - glutamyl-tRNA synthetase

Escherichia coli O157:H7 str. Sakai

Kim, S.I. et al., Skouloubris, S. et al., Salazar, J.C. et al., Lapointe, J. et al., Sekine, S. et al., et al.

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Disease relevance of gltX

Influence of FIS on the transcription from closely spaced and non-overlapping divergent promoters for an aminoacyl-tRNA synthetase gene (gltX) and a tRNA operon (valU) in Escherichia coli [1].
Here, we report the discovery of an essential GluRS-like enzyme (GluRS2), which coexists with another GluRS (GluRS1) in Helicobacter pylori [2].
Here we report the characterization of a well conserved glutamyl-tRNA synthetase (GluRS) paralog (YadB in Escherichia coli) that is present in the genomes of >40 species of proteobacteria, cyanobacteria, and actinobacteria [3].
We demonstrate that while Acidithiobacillus ferrooxidans GluRS1 and Bacillus subtilis Q373R GluRS form Glu-tRNA(Glu), A. ferrooxidans and Helicobacter pylori GluRS2 form Glu-tRNA(Gln) in E. coli in vivo [4].
To date one crystal structure of a glutamyl-tRNA synthetase (Thermus thermophilus) has been solved [5].

High impact information on gltX

Unlike GluRS, the YadB protein was able to activate glutamate in presence of ATP in a tRNA-independent fashion and to transfer glutamate onto tRNA(Asp) [3].
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 [2].
The lack of aminoacylation of the mutant tRNA indicates that this mutant tRNA is not a substrate for the H. volcanii glutamyl-tRNA synthetase [6].
Phosphate-group protection by GluRS from ethylnitrosourea was observed most strongly for the minor groove side of D-stem helix, indicating that GluRs tightly binds to the D stem for recognition, on the minor groove side, of the potent identity-determinant groups of the U11.A24 and U13.G22 base-pairs [7].
The 5' region of these mRNAs can adopt a stable secondary structure (close to the ribosome binding site) that is similar to the anticodon and part of the dihydroU stems and loops of tRNA(Glu), and which might be involved in translational regulation of GluRS synthesis [8].

Chemical compound and disease context of gltX

However, in the presence of E. coli tRNAGlu, GluRS binds specifically with L-glutamate [9].
By in vitro aminoacylation of these hybrid tRNA molecules and of tRNAs with base substitutions at positions of nucleotide modification, we show conclusively that the modified uridine at position 34 in tRNA(Glu) is required for efficient aminoacylation by E. coli GluRS [10].
The Bacillus subtilis glutamyl-tRNA synthetase (GluRS), encoded by the gltX gene, aminoacylates its homologous tRNA(Glu) and tRNA(Gln) with glutamate [11].
All of the E. coli glutamine tRNAs containing U34 such as tRNA1(Gln), tRNA2(Gln) (AU), and tRNA2(Gln) (12M) could be charged with glutamate by GluRS (bs), whereas tRNA2(Gln) (ec) and its T-stem mutant tRNA2(Gln) (M21) containing C34 could not be charged by the same enzyme [12].
To ascertain whether E. coli growth inhibition caused by B. subtilis GluRS synthesis is a consequence of Glu-tRNA1 Ghn formation, we constructed an in vivo test system, in which B. subtilis GluRS gene expression is controlled by IPTG [13].

Biological context of gltX

Phylogenetic analyses predict that GlnRS arose from glutamyl-tRNA synthetase (GluRS), via gene duplication with subsequent evolution of specificity [2].
The GluRS purified from the ts mutant strain EM111-ts1 has the same stability as the wild-type enzyme, but its Km forglutamate increases with the temperature, suggesting that the locus gltE codes for a regulatory factor, possibly for the polypeptide chain that is co-purified with the catalytic subunit [14].

Anatomical context of gltX

In bacteria, archaea and eukaryotic organelles, the formation of Gln-tRNA(Gln) is prevalently accomplished by a transamidation pathway, aminoacylation of tRNA(Gln) with Glu by glutamyl-tRNA synthetase (GluRS) followed by a tRNA-dependent transamidation of Glu from Glu-tRNA(Gln) [15].

Associations of gltX with chemical compounds

These mutants were examined for aminoacylation in vitro with GlnRS and also with glutamyl-tRNA synthetase (GluRS) to correlate gains in glutamine acceptance with losses of glutamate acceptance [16].
In the presence of tRNAGlu, the GluRS C100Y variant has a lower affinity for l-glutamate than the wild-type enzyme, with Km and Kd values increased 12- and 20-fold, respectively [17].
To find out whether modified bases in tRNA(Gln) (bs) are involved in the recognition by GluRS (bs), glutamylation of tRNA(Gln) (bs) produced by in vitro transcription was also examined but the in vitro transcript of tRNA(Gln) (bs) could not be charged with glutamic acid by GluRS (bs) [12].

Analytical, diagnostic and therapeutic context of gltX

In an attempt to evaluate the contribution of these effects and that of true asynchronisms on 2D maps, the heat-induced aggregation of glutamyl-tRNA synthetase (GluRS) was studied as a typical example of the application of Fourier transform infrared (FTIR) spectroscopy in the amide I region [18].

References

Influence of FIS on the transcription from closely spaced and non-overlapping divergent promoters for an aminoacyl-tRNA synthetase gene (gltX) and a tRNA operon (valU) in Escherichia coli. Champagne, N., Lapointe, J. Mol. Microbiol. (1998) [Pubmed]
A noncognate aminoacyl-tRNA synthetase that may resolve a missing link in protein evolution. Skouloubris, S., Ribas de Pouplana, L., De Reuse, H., Hendrickson, T.L. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
A truncated aminoacyl-tRNA synthetase modifies RNA. Salazar, J.C., Ambrogelly, A., Crain, P.F., McCloskey, J.A., Söll, D. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
In vivo formation of glutamyl-tRNA(Gln) in Escherichia coli by heterologous glutamyl-tRNA synthetases. Núñez, H., Lefimil, C., Min, B., Söll, D., Orellana, O. FEBS Lett. (2004) [Pubmed]
Glutamyl-tRNA sythetase. Freist, W., Gauss, D.H., Söll, D., Lapointe, J. Biol. Chem. (1997) [Pubmed]
Importance of the anticodon sequence in the aminoacylation of tRNAs by methionyl-tRNA synthetase and by valyl-tRNA synthetase in an Archaebacterium. Ramesh, V., RajBhandary, U.L. J. Biol. Chem. (2001) [Pubmed]
Major identity determinants in the "augmented D helix" of tRNA(Glu) from Escherichia coli. Sekine, S., Nureki, O., Sakamoto, K., Niimi, T., Tateno, M., Go, M., Kohno, T., Brisson, A., Lapointe, J., Yokoyama, S. J. Mol. Biol. (1996) [Pubmed]
Closely spaced and divergent promoters for an aminoacyl-tRNA synthetase gene and a tRNA operon in Escherichia coli. Transcriptional and post-transcriptional regulation of gltX, valU and alaW. Brun, Y.V., Sanfaçon, H., Breton, R., Lapointe, J. J. Mol. Biol. (1990) [Pubmed]
Conformation change of tRNAGlu in the complex with glutamyl-tRNA synthetase is required for the specific binding of L-glutamate. Hara-Yokoyama, M., Yokoyama, S., Miyazawa, T. Biochemistry (1986) [Pubmed]
A 2-thiouridine derivative in tRNAGlu is a positive determinant for aminoacylation by Escherichia coli glutamyl-tRNA synthetase. Sylvers, L.A., Rogers, K.C., Shimizu, M., Ohtsuka, E., Söll, D. Biochemistry (1993) [Pubmed]
Overproduction of the Bacillus subtilis glutamyl-tRNA synthetase in its host and its toxicity to Escherichia coli. Pelchat, M., Lacoste, L., Yang, F., Lapointe, J. Can. J. Microbiol. (1998) [Pubmed]
Major identity element of glutamine tRNAs from Bacillus subtilis and Escherichia coli in the reaction with B. subtilis glutamyl-tRNA synthetase. Kim, S.I., Söll, D. Mol. Cells (1998) [Pubmed]
Growth inhibition of Escherichia coli during heterologous expression of Bacillus subtilis glutamyl-tRNA synthetase that catalyzes the formation of mischarged glutamyl-tRNA1 Gln. Baick, J.W., Yoon, J.H., Namgoong, S., Söll, D., Kim, S.I., Eom, S.H., Hong, K.W. J. Microbiol. (2004) [Pubmed]
Thermosensitive mutants of Escherichia coli K-12 altered in the catalytic Subunit and in a Regulatory factor of the glutamy-transfer ribonucleic acid synthetase. Lapointe, J., Delcuve, G. J. Bacteriol. (1975) [Pubmed]
Modular evolution of the Glx-tRNA synthetase family--rooting of the evolutionary tree between the bacteria and archaea/eukarya branches. Siatecka, M., Rozek, M., Barciszewski, J., Mirande, M. Eur. J. Biochem. (1998) [Pubmed]
Discrimination among tRNAs intermediate in glutamate and glutamine acceptor identity. Rogers, K.C., Söll, D. Biochemistry (1993) [Pubmed]
The zinc-binding site of a class I aminoacyl-tRNA synthetase is a SWIM domain that modulates amino acid binding via the tRNA acceptor arm. Banerjee, R., Dubois, D.Y., Gauthier, J., Lin, S.X., Roy, S., Lapointe, J. Eur. J. Biochem. (2004) [Pubmed]
Study of protein aggregation using two-dimensional correlation infrared spectroscopy and spectral simulations. Lefèvre, T., Arseneault, K., Pézolet, M. Biopolymers (2004) [Pubmed]

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