Imprints of the genetic code

Imprints of the genetic code in the ribosome

The establishment of the genetic code remains elusive nearly five decades after the code was elucidated. The stereochemical hypothesis postulates that the code developed from interactions between nucleotides and amino acids, yet supporting evidence in a biological context is lacking.

Figure 4.1: Ribosome serves as a molecular fossil revealing secrets of code origin and evolution

We discovered that anticodons are selectively enriched near their respective amino acids in the ribosome, and that such enrichment is significantly correlated with the canonical code over random codes. Ribosomal anticodon-amino acid enrichment further reveals that specific codons were reassigned during code evolution, and that the code evolved through a two-stage transition from ancient amino acids without anticodon interaction to newer additions with anticodon interaction. Our discovery provides biological evidence to support the stereochemical theory and advancing it by pinpointing the nucleotides to anticodons (not codons). We further proposed a new “two-stage transition” model for code origin.

References

Johnson, D.B.F., Wang, L.*, Imprints of the genetic code in the ribosome. Proc. Natl. Acad. Sci. U.S.A. 107: 8298-8303 (2010). PMCID: PMC2889578.