Team:TU Eindhoven/Background/Orthogonal

Orthogonal tRNA System

Normally, all proteins produced by a cell are built with the 20 amino acids naturally present in cells. However protein engineering has made the incorporation of unnatural amino acids possible. This is done with the use of orthogonal tRNA aminoacyl-tRNA synthetase and tRNA pairs, an orthogonal system does not interfere with any other system in the cell. The anticodon on the tRNA corresponds with the TAG codon (amber stop codon). This codon has to be placed in the gene of interest to incorporate the unnatural amino acid.

The aminoacyl-tRNA synthetase is specifically modified to bind the unnatural amino acid to the orthogonal tRNA. The tRNA, in response to an amber stop codon(UAG) on the mRNA, incorporates the unnatural amino acid into the amino acid sequence (Figure 2)

Figure 1. The incorporation of an unnatural amino acid into a protein.

Bibliography

Davis, Lloyd, and Jason W. Chin. "Designer proteins: applications of genetic code expansion in cell biology."Nature Reviews Molecular Cell Biology 13 (2012): 168-182.