2ag6

Publication Abstract from PubMed

Recently, tRNA aminoacyl-tRNA synthetase pairs have been evolved that allow one to genetically encode a large array of unnatural amino acids in both prokaryotic and eukaryotic organisms. We have determined the crystal structures of two substrate-bound Methanococcus jannaschii tyrosyl aminoacyl-tRNA synthetases that charge the unnatural amino acids p-bromophenylalanine and 3-(2-naphthyl)alanine (NpAla). A comparison of these structures with the substrate-bound WT synthetase, as well as a mutant synthetase that charges p-acetylphenylalanine, shows that altered specificity is due to both side-chain and backbone rearrangements within the active site that modify hydrogen bonds and packing interactions with substrate, as well as disrupt the alpha8-helix, which spans the WT active site. The high degree of structural plasticity that is observed in these aminoacyl-tRNA synthetases is rarely found in other mutant enzymes with altered specificities and provides an explanation for the surprising adaptability of the genetic code to novel amino acids.

Structural plasticity of an aminoacyl-tRNA synthetase active site.,Turner JM, Graziano J, Spraggon G, Schultz PG Proc Natl Acad Sci U S A. 2006 Apr 25;103(17):6483-8. Epub 2006 Apr 17. PMID:16618920^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.