Amino Acid Composition of Proteins as a Product of Molecular Evolution

Science  08 Oct 1971:
Vol. 174, Issue 4005, pp. 150-153
DOI: 10.1126/science.174.4005.150


The average amino acid composition of proteins is determined by the genetic code and by random base changes in evolution. Small but significant deviations from expected composition can be explained by selective constraint on amino acid substitutions. In particular, the deficiency of arginine in proteins has been caused by constraint, during evolution, on fixation of mutations substituting arginine for other amino acids.