Patterns of distribution of modified nucleotides at position 37 in E. coli, S. cerevisiae and five archaeal species on the wheels of the genetic code (Grosjean and Westhof 2016). In that representation, GC-rich codons are at the top and AU-rich at the bottom of the wheel. The codon positions are numbered 1, 2, 3 so that G1A2C3 gives an Asp codon. The four quadrants are characterized by the first codon position. Data for E. coli and S. cerevisiae are from MODOMICS (Boccaletto et al. 2018). Data for H. volcanii are from Gupta (1984, 1986) and Grosjean et al. (2008a), data for M. jannaschii are from Yu et al. (2019). The wheels for E. coli, S. cerevisiae, and H. volcanii are adapted from Grosjean and Westhof (2016). In each quadrant, the observed modified nucleotides at position 37 are shown (red for G derivatives and black for A derivatives; the very unusual U37 of tRNA-Ala(GGC) of M. jannaschii is also shown in black). The modifications observed frequently have a large font and are bold, while those observed only once or in a single tRNA species have a smaller font and are not bold.
