(a) Chemical structure of natural substrates
of class Ia AARSs
and putative fluorinated analogues. 1: (2S)-4,4,4-trifluoroethylglycine
(TfeGly), 2: (2S)-4,4-difluoroethylglycine (DfeGly),
3: (2S)-4-monofluoroethylglycine (MfeGly), 4: (2S)-4,4-difluoropropylglycine (DfpGly), 5: (2S,4S,4R)-5,5,5-trifluoroleucine
(TfLeu), 6: (2S)-5,5,5,5′,5′,5′-hexafluoroleucine
(HfLeu), 7: (2S,2R)-3,3,3-trifluoroalanine
(TfAla), 8: (2S,3R)-4,4,4-trifluorovaline
((2S,3R)-TfVal), 9: (2S,3S)-4,4,4-trifluorovaline ((2S,3S)-TfVal), 10: (2S,2R)-4,4,4,4′,4′,4′-hexafluorovaline (HfVal), 11:
(2S,2R)-6,6,6-trifluoronorleucine
(TfNLeu), (b) Kinetic data that were determined in this study for
the activation of these fluorinated AAs by the indicated class Ia
AARSs.