SYNTHETIC POLYNUCLEOTIDES AND THE AMINO ACID CODE, V

Abstract

Hypo-xanthine can replace guanine in amino acid coding for, like poly UG (5:1), poly UI (5:1) stimulated the incorporation of cysteine, glycine, leucine, tryptophan, and valine into acid-insoluble products in the E. coli system to the same relative extent. Treatment of synthetic polynucleotides with nitrous acid modified their coding characteristics as expected from the deamination of adenine to hypoxanthine and cytosine to uracil. Poly UA lost its coding specificity and acquired that of poly UI, and poly UC lost its activity to stimulate the incorporation of serine but not that of phenylalanine. Deamination of guanine to xanthine, by treatment of poly UG with nitrous acid, wiped out the activity of this polymer to stimulate valine incorporation. Thus, contrary to hypoxanthine, xanthine cannot replace guanine in amino acid coding.