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Review
Aminoacyl-tRNA Synthesis by Pre-Translational Amino Acid Modification
Liang Feng, Kelly Sheppard, Suk Namgoong, Alexandre Ambrogelly, Carla Polycarpo,Lennart Randau, Debra Tumbula-Hansena and Dieter Söll
volume 1 | issue 1
may/june 2004Pages: 16 - 20
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Aminoacyl-tRNAs (aa-tRNAs) are essential substrates for ribosomal translation, and are generally synthesized by aminoacyl-tRNA synthetases (aaRSs). It was expected earlier that every organism would contain a complete set of twenty aaRSs, one for each canonical amino acid. However, analysis of the many known genome sequences and biochemical studies revealed that most organisms lack asparaginyl- and glutaminyl-tRNA synthetases, and thus are unable to attach asparagine and glutamine directly onto their corresponding tRNA. Instead, a pre-translational amino acid modification is required to convert Asp-tRNAAsn and Glu-tRNAGln to the correctly charged Asn-tRNAAsn and Gln-tRNAGln, respectively. This transamidation pathway of amide aa-tRNA synthesis is common in most bacteria and archaea. Unexpected results from biochemical, genetic and genomic studies showed that a large variety of different bacteria rely on tRNA-dependent transamidation for the formation of the amino acid asparagine. Pre-translational modifications are not restricted to asparagine and glutamine but are also found in the biosynthesis of some other aa-tRNAs, such as the initiator tRNA fmettRNAMeti and Sec-tRNASec specifying selenocysteine, the 21st co-translationally inserted amino acid. tRNA-dependent amino acid modification is also involved in the generation of aminolevulinic acid, the first precursor for porphyrin biosynthesis in many organisms.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.