1. Genetic Code: Introducing Pyrrolysine
Michael Ibba, Dieter Söll 
Current Biology 
Volume 12, Issue 13, Pages R464-R466 (July 2002)
DOI: /S (02)

2. Figure 1
The structures of pyrrolysine and lysine. X indicates a methyl, ammonium or hydroxyl group.
Current Biology  , R464-R466DOI: ( /S (02) )

3. Figure 2
Putative scheme for the co-translational insertion of pyrrolysine at amber codons.
An amber suppressing tRNA (tRNACUA) is first charged with lysine by PylS to give Lys-tRNACUA. Lys-tRNACUA undergoes pre-translational modification to produce Pyl-tRNACUA which is then used for the translation on in-frame amber codons during ribosomal protein synthesis.
Current Biology  , R464-R466DOI: ( /S (02) )