Dieter Söll: "The Continued Evolution of the Genetic Code"

Dieter Söll
Sterling Professor of Molecular Biophysics and Biochemistry, Department of Molecular Biophysics and Biochemistry, Yale University

The Continued Evolution of the Genetic Code

At the time of its elucidation the genetic code with 20 amino acids was suggested to be universal in all organisms, and the result of a ‘frozen accident’ unable to evolve further. How do we see the genetic code today – 45 years later? There are 22 natural amino acids: selenocysteine, the 21st, and pyrrolysine, the 22nd, are directly inserted into proteins during translation. Selenocysteine is synthesized via a tRNA-dependent pathway and decodes UGA (opal) codons. In contrast, pyrrolysine is ligated directly to a suppressor tRNAPyl and inserted into proteins in response to UAG (amber) codons. Based on the realization that protein plasticity is a feature of living cells, man-made expansion of the genetic code has begun by adding non-standard amino acids (e.g., phosphoserine, N-acetyl-lysine) to the repertoire of the cell. These present evolutionary developments are the underpinning for the creation of new organisms in the realm of synthetic biology.