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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Crystal Structure of a Non-discriminating Glutamyl-tRNA Synthetase.

Error-free protein biosynthesis is dependent on the reliable charging of each tRNA with its cognate amino acid. Many bacteria, however, lack a glutaminyl-tRNA synthetase. In these organisms, tRNA(Gln) is initially mischarged with glutamate by a non-discriminating glutamyl-tRNA synthetase (ND-GluRS). This enzyme thus charges both tRNA(Glu) and tRNA(Gln) with glutamate. Discriminating GluRS (D-GluRS), found in some bacteria and all eukaryotes, exclusively generates Glu-tRNA(Glu). Here we present the first crystal structure of a non-discriminating GluRS from Thermosynechococcus elongatus (ND-GluRS(Tel)) in complex with glutamate at a resolution of 2.45 A. Structurally, the enzyme shares the overall architecture of the discriminating GluRS from Thermus thermophilus (D-GluRS(Tth)). We confirm experimentally that GluRS(Tel) is non-discriminating and present kinetic parameters for synthesis of Glu-tRNA(Glu) and of Glu-tRNA(Gln). Anticodons of tRNA(Glu) ((34)C/UUC(36)) and tRNA(Gln) ((34)C/UUG(36)) differ only in base 36. The pyrimidine base of C36 is specifically recognized in D-GluRS(Tth) by the residue Arg358. In ND-GluRS(Tel) this arginine residue is replaced by glycine (Gly366) presumably allowing both cytosine and the bulkier purine base G36 of tRNA(Gln) to be tolerated. Most other ND-GluRS share this structural feature, leading to relaxed substrate specificity.[1]

References

  1. Crystal Structure of a Non-discriminating Glutamyl-tRNA Synthetase. Schulze, J.O., Masoumi, A., Nickel, D., Jahn, M., Jahn, D., Schubert, W.D., Heinz, D.W. J. Mol. Biol. (2006) [Pubmed]
 
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