Expanding the substrate scope of pyrrolysyl-transfer RNA synthetase enzymes to include non-alpha-amino acids in vitro and in vivo.
Fricke, R., Swenson, C.V., Roe, L.T., Hamlish, N.X., Shah, B., Zhang, Z., Ficaretta, E., Ad, O., Smaga, S., Gee, C.L., Chatterjee, A., Schepartz, A.(2023) Nat Chem 15: 960-971
- PubMed: 37264106 
- DOI: https://doi.org/10.1038/s41557-023-01224-y
- Primary Citation of Related Structures:  
7U0R - PubMed Abstract: 
The absence of orthogonal aminoacyl-transfer RNA (tRNA) synthetases that accept non-L-α-amino acids is a primary bottleneck hindering the in vivo translation of sequence-defined hetero-oligomers and biomaterials. Here we report that pyrrolysyl-tRNA synthetase (PylRS) and certain PylRS variants accept α-hydroxy, α-thio and N-formyl-L-α-amino acids, as well as α-carboxy acid monomers that are precursors to polyketide natural products. These monomers are accommodated and accepted by the translation apparatus in vitro; those with reactive nucleophiles are incorporated into proteins in vivo. High-resolution structural analysis of the complex formed between one PylRS enzyme and a m-substituted 2-benzylmalonic acid derivative revealed an active site that discriminates prochiral carboxylates and accommodates the large size and distinct electrostatics of an α-carboxy substituent. This work emphasizes the potential of PylRS-derived enzymes for acylating tRNA with monomers whose α-substituent diverges substantially from the α-amine of proteinogenic amino acids. These enzymes or derivatives thereof could synergize with natural or evolved ribosomes and/or translation factors to generate diverse sequence-defined non-protein heteropolymers.
Organizational Affiliation: 
Department of Chemistry, University of California, Berkeley, CA, USA.