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Updated: Aug 18, 2026

Residue-specific Incorporation of Noncanonical Amino Acids into Model Proteins Using an Escherichia coli Cell-free Transcription-translation System
Published on: August 1, 2016
Selenocysteine, a highly specific component of certain enzymes, is incorporated by a UGA-directed co-translational
1Institut für Genetik und Mikrobiologie, Universität München, FRG.
Abstract:
The opal termination codon UGA is used in both prokaryotic and eukaryotic species to direct the specific insertion of selenocysteine into certain selenium-dependent enzymes. So far a formate dehydrogenase (hydrogenase-linked) of Escherichia coli and glutathione peroxidases of murine, human and rat origin have been identified as enzymes containing selenocysteine residues encoded by UGA. A novel seryl-tRNA, anticodon UCA, that specifically recognizes the UGA codon is required for selenocysteine incorporation into formate dehydrogenase. A eukaryotic UGA suppressor tRNA with UCA anticodon that accepts serine and is phosphorylated to O-phosphoseryl-tRNA may have a corresponding function in glutathione peroxidase synthesis. Other factors required for the unusual usage of the in-frame UGA codons to specify selenocysteine incorporation and the biochemical mechanism involved in distinguishing these from normal UGA termination codons are discussed.
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