Facile Recoding of Selenocysteine in Nature |
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| Authors: | Dr Takahito Mukai Dr Markus Englert Dr H James Tripp Dr Corwin Miller Dr Natalia N Ivanova Dr Edward M Rubin Dr Nikos C Kyrpides Prof Dieter Söll |
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| Affiliation: | 1. Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA;2. Department of Energy Joint Genome Institute (DOE JGI), Walnut Creek, CA, USA;3. Department of Chemistry, Yale University, New Haven, CT, USA |
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| Abstract: | Selenocysteine (Sec or U) is encoded by UGA, a stop codon reassigned by a Sec‐specific elongation factor and a distinctive RNA structure. To discover possible code variations in extant organisms we analyzed 6.4 trillion base pairs of metagenomic sequences and 24 903 microbial genomes for tRNASec species. As expected, UGA is the predominant Sec codon in use. We also found tRNASec species that recognize the stop codons UAG and UAA, and ten sense codons. Selenoprotein synthesis programmed by UAG in Geodermatophilus and Blastococcus, and by the Cys codon UGU in Aeromonas salmonicida was confirmed by metabolic labeling with 75Se or mass spectrometry. Other tRNASec species with different anticodons enabled E. coli to synthesize active formate dehydrogenase H, a selenoenzyme. This illustrates the ease by which the genetic code may evolve new coding schemes, possibly aiding organisms to adapt to changing environments, and show the genetic code is much more flexible than previously thought. |
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| Keywords: | genetic code metagenome selenocysteine sense codon recoding synthetic biology |
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