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I am trying to understand the prehistory of amino acids in cells.
All living cells now use 20 (or 22 if you include selenocysteine and pyrrolysine) amino acids. Perhaps in the past there were fewer amino acids used in cells, especially if the theory of a 2-nucleotide codon is to be believed.
Is there any theory as to the order in which these amino acids were incorporated into cells?
This paper (by Akanuma, Kigawi, Yokoyama, "Combinatorial mutagenesis to restrict amino acid usage in an enzyme to a reduced set", http://www.pnas.org/content/99/21/13549.full suggest that the full complement of 20 amino acids are not strictly necessary by reducing the number of amino acids in a certain enzyme to 13, yet still retain functionality.
All living cells now use 20 (or 22 if you include selenocysteine and pyrrolysine) amino acids. Perhaps in the past there were fewer amino acids used in cells, especially if the theory of a 2-nucleotide codon is to be believed.
Is there any theory as to the order in which these amino acids were incorporated into cells?
This paper (by Akanuma, Kigawi, Yokoyama, "Combinatorial mutagenesis to restrict amino acid usage in an enzyme to a reduced set", http://www.pnas.org/content/99/21/13549.full suggest that the full complement of 20 amino acids are not strictly necessary by reducing the number of amino acids in a certain enzyme to 13, yet still retain functionality.