Tuning phenylalanine fluorination to assess aromatic contributions to protein function and stability in cells

Nat Commun. 2023 Jan 4;14(1):59. doi: 10.1038/s41467-022-35761-w.


The aromatic side-chains of phenylalanine, tyrosine, and tryptophan interact with their environments via both hydrophobic and electrostatic interactions. Determining the extent to which these contribute to protein function and stability is not possible with conventional mutagenesis. Serial fluorination of a given aromatic is a validated method in vitro and in silico to specifically alter electrostatic characteristics, but this approach is restricted to a select few experimental systems. Here, we report a group of pyrrolysine-based aminoacyl-tRNA synthetase/tRNA pairs (tRNA/RS pairs) that enable the site-specific encoding of a varied spectrum of fluorinated phenylalanine amino acids in E. coli and mammalian (HEK 293T) cells. By allowing the cross-kingdom expression of proteins bearing these unnatural amino acids at biochemical scale, these tools may potentially enable the study of biological mechanisms which utilize aromatic interactions in structural and cellular contexts.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acids / metabolism
  • Amino Acyl-tRNA Synthetases* / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • HEK293 Cells
  • Halogenation
  • Humans
  • Phenylalanine* / metabolism
  • RNA, Transfer / metabolism


  • Amino Acids
  • Amino Acyl-tRNA Synthetases
  • Phenylalanine
  • RNA, Transfer