Structural and functional analysis of Glutaminyl-tRNA synthetase (TtGlnRS) from Thermus thermophilus HB8 and its complexes

Aminoacyl-tRNA synthetases (AaRSs) are vital enzymes for translation of proteins in cells. AaRSs catalyse the esterification of a specific amino acid to corresponding tRNAs to form an aminoacyl-tRNA that is used in ribosome-based protein synthesis. We focused on Glutaminyl tRNA synthetase (GlnRS) enzyme from the extreme thermophile Thermus thermophilus for structural studies. Our thermal shift assays show binding of enzyme substrates L-Gln and ATP as well as of various metals including cesium. We resolved crystal structures of apo-GlnRS as well as those in complex with AMP and ATP at 2.8 Å, 2.4 Å and 2.6 Å respectively. The bound cesium was found at the site of magnesium that typically binds to GlnRS. High structural conservation was evident in the Thermus thermophilus GlnRS when compared to those from Escherichia coli GlnRS.