NUCLEOTIDE BASE CODING AND AMINO ACID REPLACEMENTS IN PROTEINS

Abstract

Known amino acid replacements in mutants of human hemoglobin are consistent with a single base change in the known triplet codes. Certain amino acid replacements in homologous proteins of various species also involve single base changes whereas others do not; the latter probably involve stepwise multiple mutation. The data suggest that for 16 amino acids, uracil occupies the same but unknown position in the codes; the four other codes must involve a different location of uracil in the triplet. Problems of the maintenance and evolution of peptide and protein structure and function are discussed briefly.