Anticodon-binding domain swapping in a nondiscriminating aspartyl-tRNA synthetase reveals contributions to tRNA specificity and catalytic activity.

The nondiscriminating aspartyl-tRNA synthetase (ND-AspRS), found in many archaea and bacteria, covalently attaches aspartic acid to tRNA and tRNA generating a correctly charged Asp-tRNA and an erroneous Asp-tRNA . This relaxed tRNA specificity is governed by interactions between the tRNA and the enzyme. In an effort to assess the contributions of the anticodon-binding domain to tRNA specificity, we constructed two chimeric enzymes, Chimera-D and Chimera-N, by replacing the native anticodon-binding domain in the Helicobacter pylori ND-AspRS with that of a discriminating AspRS (Chimera-D) and an asparaginyl-tRNA synthetase (AsnRS, Chimera-N), both from Escherichia coli.

Crystal structure of the N-terminal anticodon-binding domain of the nondiscriminating aspartyl-tRNA synthetase from Helicobacter pylori.

The N-terminal anticodon-binding domain of the nondiscriminating aspartyl-tRNA synthetase (ND-AspRS) plays a crucial role in the recognition of both tRNA and tRNA. Here, the first X-ray crystal structure of the N-terminal domain of this enzyme (ND-AspRS) from the human-pathogenic bacterium Helicobacter pylori is reported at 2.0 Å resolution.

Overproduction of the N-terminal anticodon-binding domain of the non-discriminating aspartyl-tRNA synthetase from Helicobacter pylori for crystallization and NMR measurements.

Aminoacyl-tRNA synthetases (aaRSs) covalently attach an amino acid to its cognate tRNA isoacceptors through an ester bond. The standard set of 20 amino acids implies 20 aaRSs for each pair of amino acid/tRNA isoacceptors. However, the genomes of all archaea and some bacteria do not encode for a complete set of 20 aaRSs.