Evolution of Amino Acid Frequencies in Proteins Over Deep Time: Inferred Order of Introduction of Amino Acids into the Genetic Code

Dawn J. Brooks, Jacques R. Fresco, Arthur M. Lesk, Mona Singh
2002 Molecular biology and evolution  
To understand more fully how amino acid composition of proteins has changed over the course of evolution, a method has been developed for estimating the composition of proteins in an ancestral genome. Estimates are based upon the composition of conserved residues in descendant sequences and empirical knowledge of the relative probability of conservation of various amino acids. Simulations are used to model and correct for errors in the estimates. The method was used to infer the amino acid
more » ... the amino acid composition of a large protein set in the Last Universal Ancestor (LUA) of all extant species. Relative to the modern protein set, LUA proteins were found to be generally richer in those amino acids that are believed to have been most abundant in the prebiotic environment and poorer in those amino acids that are believed to have been unavailable or scarce. It is proposed that the inferred amino acid composition of proteins in the LUA probably reflects historical events in the establishment of the genetic code. Abbreviations: MP, maximum parsimony; ML, maximum likelihood; LUA, Last Universal Ancestor; COG, Clusters of Orthologous Groups.
doi:10.1093/oxfordjournals.molbev.a003988 pmid:12270892 fatcat:4gty45ceq5dybdldhzvb2rcmea