The Structure and Dynamics of Eukaryotic Glutaminyl-tRNA Synthetase
May 2013 SSRL Science
Summary by Lori Ann White, SLAC Office of Communications
Full-length Gln4 shown bound to tRNAgln |
Aminoacyl-tRNA synthetases are required in all three domains of life to add
the correct amino acid to its cognate tRNA, an essential step in protein
synthesis. Despite their importance, no structure had been reported for any
full-length eukaryotic, glutaminyl-tRNA synthetase (GlnRS), although structural
data for two prokaryotic GlnRS species exists. A group led by Edward Snell of
the Hauptman-Woodward Medical Research Institute has recently used data from
SSRL to develop a model of the full-length enzyme in solution.
Using crystallographic structures and homology with known complexes, they also
modeled the full-length enzyme bound to tRNAgln.
Two basic pathways exist for aminoacylation of glutamine: In eukaryotes and
some bacteria, the glutaminyl-tRNA synthetase (GlnRS) binds to
tRNAgln, glutamine and ATP and first forms a glutaminyl adenylate
molecule that is then covalently attached to the 3’-end of
tRNAgln with the release of AMP, while in most bacteria and all
archaea a non-discriminating glutamyl-tRNA synthetase (GluRS) attaches glutamic
acid to both tRNAglu and tRNAgln. The misacylated
glu-tRNAgln is then converted to gln-tRNAgln by the
GatCAB amidotransferase enzyme in bacteria and some archaea, or by the GatDE
amidotransferases in other archaea.
Using remotely collected macromolecular crystallography data from SSRL,
Snell's group first determined the structure of the N-terminal domain (NTD)
for the specific glutaminyl-tRNA synthetase (ScGlnRS) found in the
eukaryote Saccharomyces cerevisiae, revealing that it has an
extraordinary structural resemblance to the region of the B subunit of the
GatCAB amidotransferase that binds to tRNAgln. Using SSRL Beam Line
11-1, Snell's group next determined the crystal structure of the C-terminal domain
(CTD) of ScGlnRS. This structure, the structure of the NTD and small
angle x-ray scattering (SAXS) data measured at SSRL Beam Line 4-2 enabled
Snell's group to create their model of the full-length enzyme in solution.
This model, combined with the model of the full-length enzyme bound to
tRNAgln, suggests that C-terminal domain-binding to tRNA results in a
large conformational reorientation of the N-terminal domain, enabling
interactions between it and the tRNA. The combination of crystallographic and
solution studies enabled by SSRL facilities has yielded fundamental new
insights into the structural rearrangements occurring in eukaryotic
GlnRS-tRNAgln complex formation.
Primary Citations
T. D. Grant, J. R. Luft, J. R. Wolfley, M. E. Snell, H. Tsuruta, S. Corretore, E. Quartley, E. M. Phizicky, E. J. Grayhack and E. H. Snell, "The Structure of Yeast Glutaminyl-tRNA Synthetase and Modeling of Its Interaction with tRNA", J. Mol. Biol. (2013) doi: 10.1016/j.jmb.2013.03.043
Related Links
- Science Highlight – HTML / PDF
- SSRL Science Highlights Archive
- SSRL Beam Lines
Contact
Edward Snell, SUNY Buffalo / Hauptman-Woodward Medical Research Institute
