Nucleic Acids Research Advance Access originally published online on February 5, 2008
Nucleic Acids Research 2008 36(6):1813-1825; doi:10.1093/nar/gkn015
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Nucleic Acids Research, 2008, Vol. 36, No. 6 1813-1825
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
From one amino acid to another: tRNA-dependent amino acid biosynthesis
1Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520–8114, USA, 2Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland and 3Department of Chemistry, Yale University, New Haven, CT 06520–8114, USA
*To whom correspondence should be addressed. Tel: 203 432 6200; Fax: 203 432 6202; Email: dieter.soll{at}yale.edu
Received December 21, 2007. Revised January 8, 2008. Accepted January 9, 2008.
Aminoacyl-tRNAs (aa-tRNAs) are the essential substrates for translation. Most aa-tRNAs are formed by direct aminoacylation of tRNA catalyzed by aminoacyl-tRNA synthetases. However, a smaller number of aa-tRNAs (Asn-tRNA, Gln-tRNA, Cys-tRNA and Sec-tRNA) are made by synthesizing the amino acid on the tRNA by first attaching a non-cognate amino acid to the tRNA, which is then converted to the cognate one catalyzed by tRNA-dependent modifying enzymes. Asn-tRNA or Gln-tRNA formation in most prokaryotes requires amidation of Asp-tRNA or Glu-tRNA by amidotransferases that couple an amidase or an asparaginase to liberate ammonia with a tRNA-dependent kinase. Both archaeal and eukaryotic Sec-tRNA biosynthesis and Cys-tRNA synthesis in methanogens require O-phosophoseryl-tRNA formation. For tRNA-dependent Cys biosynthesis, O-phosphoseryl-tRNA synthetase directly attaches the amino acid to the tRNA which is then converted to Cys by Sep-tRNA: Cys-tRNA synthase. In Sec-tRNA synthesis, O-phosphoseryl-tRNA kinase phosphorylates Ser-tRNA to form the intermediate which is then modified to Sec-tRNA by Sep-tRNA:Sec-tRNA synthase. Complex formation between enzymes in the same pathway may protect the fidelity of protein synthesis. How these tRNA-dependent amino acid biosynthetic routes are integrated into overall metabolism may explain why they are still retained in so many organisms.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
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