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Is there a twenty third amino acid in the genetic code?
Alexey V Lobanov1, Gregory V Kryukov, Dolph L Hatfield
1Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA.
Trends in Genetics : TIG
|May 23, 2006
Summary
Researchers searched for a twenty-third amino acid by analyzing archaeal and bacterial genomes for tRNAs that could read stop codons. The study found no evidence for additional widely distributed, genetically encoded amino acids beyond the 22 known.
Area of Science:
- Genetics
- Molecular Biology
- Bioinformatics
Background:
- The standard genetic code utilizes 20 common amino acids.
- Selenocysteine (Sec) and pyrrolysine (Pyl) are the 21st and 22nd amino acids, encoded by stop codons (UGA and UAG).
- The discovery of Sec and Pyl indicates the potential for expanding the genetic code by repurposing stop codons.
Purpose of the Study:
- To investigate the possibility of a genetically encoded twenty-third amino acid.
- To identify novel amino acids by reprogramming stop codons.
Main Methods:
- Utilized tRNA identification programs to scan 16 archaeal and 130 bacterial genomes.
- Searched for tRNAs with anticodons complementary to the three stop signals (UAA, UAG, UGA).
Main Results:
- Analysis of archaeal and bacterial genomes did not reveal widespread tRNAs capable of decoding stop codons for novel amino acids.
- The data suggest that the genetic code is unlikely to be expanded with additional, widely distributed amino acids.
Conclusions:
- The existence of a genetically encoded twenty-third amino acid, widely distributed across archaea and bacteria, is improbable.
- Current evidence does not support further expansion of the genetic code through stop codon reprogramming for novel amino acids.