Article
- The EMBO Journal (2004) 23, 4639 - 4648
- doi:10.1038/sj.emboj.7600474
Published online: 4 November 2004
Post-transfer editing in vitro and in vivo by the 
subunit of phenylalanyl-tRNA synthetase
Hervé Roy1, Jiqiang Ling2, Michael Irnov1 and Michael Ibba1,2
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH, USA
Correspondence to:
Michael Ibba, Department of Microbiology, The Ohio State University, 556 Bioscience Building, 484 West 12th Avenue, Columbus, OH 43210-1292, USA. Tel.: +1 614 292 2120; Fax: +1 614 292 8120; E-mail: ibba.1@osu.edu
Received 25 August 2004; Accepted 13 October 2004
Abstract
Translation of the genetic code requires attachment of tRNAs to their cognate amino acids. Errors during amino-acid activation and tRNA esterification are corrected by aminoacyl-tRNA synthetase-catalyzed editing reactions, as extensively described for aliphatic amino acids. The contribution of editing to aromatic amino-acid discrimination is less well understood. We show that phenylalanyl-tRNA synthetase misactivates tyrosine and that it subsequently corrects such errors through hydrolysis of tyrosyl-adenylate and Tyr-tRNAPhe. Structural modeling combined with an in vivo genetic screen identified the editing site in the B3/B4 domain of the 
subunit, 40 Å from the active site in the 
subunit. Replacements of residues within the editing site had no effect on Phe-tRNAPhe synthesis, but abolished hydrolysis of Tyr-tRNAPhein vitro. Expression of the corresponding mutants in Escherichia coli significantly slowed growth, and changed the activity of a recoded -galactosidase variant by misincorporating tyrosine in place of phenylalanine. This loss in aromatic amino-acid discrimination in vivo revealed that editing by phenylalanyl-tRNA synthetase is essential for faithful translation of the genetic code.
Keywords:
- editing,
- genetic code,
- phenylalanine,
- transfer RNA,
- translation
