Role of tRNA amino acid-accepting end in aminoacylation and its quality control.

ABSTRACT: Aminoacyl-tRNA synthetases (aaRSs) are remarkable enzymes that are in charge of the accurate recognition and ligation of amino acids and tRNA molecules. The greatest difficulty in accurate aminoacylation appears to be in discriminating between highly similar amino acids. To reduce mischarging of tRNAs by non-cognate amino acids, aaRSs have evolved an editing activity in a second active site to cleave the incorrect aminoacyl-tRNAs. Editing occurs after translocation of the aminoacyl-CCA?? end to the editing site, switching between a hairpin and a helical conformation for aminoacylation and editing. Here, we studied the consequence of nucleotide changes in the CCA?? accepting end of tRNA(Leu) during the aminoacylation and editing reactions. The analysis showed that the terminal A?? is essential for both reactions, suggesting that critical interactions occur in the two catalytic sites. Substitutions of C?? and C?? selectively decreased aminoacylation keeping nearly unaffected editing. These mutations might favor the regular helical conformation required to reach the editing site. Mutating the editing domain residues that contribute to CCA?? binding reduced the aminoacylation fidelity leading to cell-toxicity in the presence of non-cognate amino acids. Collectively, the data show how protein synthesis quality is controlled by the CCA?? homogeneity of tRNAs.

SUBMITTER: Zhou XL 

PROVIDER: S-EPMC3203616 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature