Figure 2.

Engineering the translational machinery to reprogramme the genetic code. (A) Creating orthogonal amber suppressor aminoacyl-tRNA synthetase/tRNA pairs. Cells contain natural synthetases (grey) that use natural amino acids (black oval) to aminoacylate natural tRNAs (black trident). Expanding the genetic code requires the addition of an orthogonal synthetase, tRNA, and amino acid (star) shown in blue. (B) Creation of orthogonal ribosome mRNA pairs by duplication and specialization. The natural cellular ribosome (grey) recognizes natural messages, while the new orthogonal ribosome (green) recognizes orthogonal messages (purple). (C) Evolving the orthogonal ribosome for quadruplet decoding for a parallel genetic code.