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J Biol Chem. 2003 Mar 14;278(11):9683-90. Epub 2002 Dec 13.

Yeast tRNA(Asp) charging accuracy is threatened by the N-terminal extension of aspartyl-tRNA synthetase.

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  • 1Département Mécanismes et Macromolécules de la Synthèse Protéique et Cristallogenèse, UPR 9002, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15 rue René Descartes, F-67084 Strasbourg Cedex, France.


This study evaluates the role of the N-terminal extension from yeast aspartyl-tRNA synthetase in tRNA aspartylation. The presence of an RNA-binding motif in this extension, conserved in eukaryotic class IIb aminoacyl-tRNA synthetases, provides nonspecific tRNA binding properties to this enzyme. Here, it is assumed that the additional contacts the 70 amino acid-long appendix of aspartyl-tRNA synthetase makes with tRNA could be important in expression of aspartate identity in yeast. Using in vitro transcripts mutated at identity positions, it is demonstrated that the extension grants better aminoacylation efficiency but reduced specificity to the synthetase, increasing considerably the risk of noncognate tRNA mischarging. Yeast tRNA(Glu(UUC)) and tRNA(Asn(GUU)) were identified as the most easily mischarged tRNA species. Both have a G at the discriminator position, and their anticodon differs only by one change from the GUC aspartate anticodon.

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