RNA CODEWORDS AND PROTEIN SYNTHESIS, VI. ON THE NUCLEOTIDE SEQUENCES OF DEGENERATE CODEWORD SETS FOR ISOLEUCINE, TYROSINE, ASPARAGINE, AND LYSINE

Abstract

To investigate nucleotide sequences of RNA codons, the tri-nucleotides ApApU, ApApC, ApApA, ApApG, ApUpU, ApUpC, UpApU, and UpApC were used as templates to direct the binding of C14-aminoacyl-sRNA to ribosomes. The results suggest that ApApU and ApApC serve as RNA codons for asparagine; ApApG and ApApA, for lysine; ApUpU and ApUpC, for isoleucine; and UpApU and UpApC, for tyrosine. Thus, two types of synonym codon pairs were observed: (1) synonym codon pairs such as XpYpU and XpYpC, and (2) a synonym pair such as XpYpA and XpYpG.