Single amino acid changes in AspRS reveal alternative routes for expanding its tRNA repertoire in vivo

Expanding tRNA recognition of a tRNA synthetase by a single amino acid change.

Aspartyl-tRNA synthetase (AspRS) occurs in two types: the discriminating enzyme (D-AspRS) forms only Asp-tRNA(Asp), whereas the nondiscriminating enzyme (ND-AspRS) also synthesizes Asp-tRNA(Asn), which is a required intermediate for protein synthesis in many organisms. We attempted to expand the tRNA recognition of the discriminating Thermococcus kodakaraensis AspRS to that of a ND-AspRS by in ...

Expanding the Amino Acid Repertoire for the Design of Novel Proteins

Amino acid modifications on tRNA.

The accurate formation of cognate aminoacyl-transfer RNAs (aa-tRNAs) is essential for the fidelity of translation. Most amino acids are esterified onto their cognate tRNA isoacceptors directly by aa-tRNA synthetases. However, in the case of four amino acids (Gln, Asn, Cys and Sec), aminoacyl-tRNAs are made through indirect pathways in many organisms across all three domains of life. The process...

A tryptophanyl-tRNA synthetase/tRNA pair for unnatural amino acid mutagenesis in E. coli.

The genetic incorporation of unnatural amino acids (UAAs) with novel structures and properties into proteins in living cells has provided a powerful new tool to both probe and modify protein structure and function. The desired UAA is encoded by a nonsense or a frameshift codon using an engineered aminoacyl-tRNA synthetase (aaRS)/tRNA pair that is orthogonal to the host cell (i.e., not cross-rea...

Alternative kynurenic acid synthesis routes studied in the rat cerebellum

Kynurenic acid (KYNA), an astrocyte-derived, endogenous antagonist of α7 nicotinic acetylcholine and excitatory amino acid receptors, regulates glutamatergic, GABAergic, cholinergic and dopaminergic neurotransmission in several regions of the rodent brain. Synthesis of KYNA in the brain and elsewhere is generally attributed to the enzymatic conversion of L-kynurenine (L-KYN) by kynurenine amino...