Engineering pyrrolysyl-trna synthetase for the incorporation of non-canonical amino acids with smaller side chains

Nikolaj G. Koch, Peter Goettig, Juri Rappsilber, Nediljko Budisa*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Site-specific incorporation of non-canonical amino acids (ncAAs) into proteins has emerged as a universal tool for systems bioengineering at the interface of chemistry, biology, and technology. The diversification of the repertoire of the genetic code has been achieved for amino acids with long and/or bulky side chains equipped with various bioorthogonal tags and useful spectral probes. Although ncAAs with relatively small side chains and similar properties are of great interest to biophysics, cell biology, and biomaterial science, they can rarely be incorporated into proteins. To address this gap, we report the engineering of PylRS variants capable of incorporating an entire library of aliphatic “small-tag” ncAAs. In particular, we performed mutational studies of a specific PylRS, designed to incorporate the shortest non-bulky ncAA (S-allyl-L-cysteine) possible to date and based on this knowledge incorporated aliphatic ncAA derivatives. In this way, we have not only increased the number of translationally active “small-tag” ncAAs, but also determined key residues responsible for maintaining orthogonality, while engineering the PylRS for these interesting substrates. Based on the known plasticity of PylRS toward different substrates, our approach further expands the reassignment capacities of this enzyme toward aliphatic amino acids with smaller side chains endowed with valuable functionalities.

Original languageEnglish
Article number11194
Number of pages17
JournalInternational Journal of Molecular Sciences
Issue number20
Publication statusPublished - 17 Oct 2021


  • aliphatic amino acids
  • azidohomoalanine
  • bioorthogonal reactive handles
  • genetic code expansion
  • non-canonical amino acids
  • photo-methionine
  • protein engineering
  • pyrrolysyl-tRNA Synthetases
  • S-allyl-L-cysteine
  • stop codon suppression


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