Journal of Molecular Evolution

, Volume 17, Issue 5, pp 273–284

Reasons for the occurrence of the twenty coded protein amino acids

  • Arthur L. Weber
  • Stanley L. Miller

DOI: 10.1007/BF01795749

Cite this article as:
Weber, A.L. & Miller, S.L. J Mol Evol (1981) 17: 273. doi:10.1007/BF01795749


Factors involved in the selection of the 20 protein L-α-amino acids during chemical evolution and the early stages of Darwinian evolution are discussed. The selection is considered on the basis of the availability in the primitive ocean, function in proteins, the stability of the amino acid and its peptides, stability to racemization, and stability on the transfer RNA. We conclude that aspartic acid, glutamic acid, arginine, lysine, serine and possibly threonine are the best choices for acidic, basic and hydroxy amino acids. The hydrophobic amino acids are reasonable choices, except for the puzzling absences ofα-amino-n-butyric acid, norvaline and norleucine. The choices of the sulfur and aromatic amino acids seem reasonable, but are not compelling. Asparagine and glutamine are apparently not primitive. If life were to arise on another planet, we would expect that the catalysts would be poly-α-amino acids and that about 75% of the amino acids would be the same as on the earth.

Key words

Amino acids Molecular evolution Genetic Code Protein synthesis Prebiotic synthesis 

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Arthur L. Weber
    • 1
  • Stanley L. Miller
    • 2
  1. 1.The Salk Institute for Biological StudiesSan DiegoUSA
  2. 2.Department of ChemistryUniversity of CaliforniaSan Diego, La JollaUSA