The Enzymatic Methylation of Ribonucleic Acid and Deoxyribonucleic Acid

Abstract

Abstract An enzyme activity which leads to the degradation of S-adenosylmethionine appears after T3 phage infection of Escherichia coli B. The purification and properties of this activity have been described. The enzyme catalyzes the conversion of S-adenosylmethionine to thiomethyladenosine and homoserine. It has been suggested that a γ-aminobutyrolactone is an intermediate in this reaction. The enzyme appears only after infection with T3 phage. Infection with phages T1, T2, T4, T5, T6, T7, or λ does not result in the appearance of any activity. The rate of enzyme formation and the requirement for protein synthesis de novo suggests that this activity is similar to early enzymes formed after infection with the T-even phages. The enzyme has been isolated both from normal phage T3-infected E. coli and from ultraviolet light-inactivated phage T3-infected E. coli. In the latter case, the specific activity of cell-free extracts was several-fold higher than extracts obtained from normal phage T3-infected cells. Infection of E. coli with ultraviolet light-inactivated phage T3 does not result in the cessation of host cell deoxyribonucleic or ribonucleic acid synthesis. Thus, newly synthesized DNA and RNA formed after infection with phage T3 are devoid of methylated bases. Phage T2, grown in ultraviolet light-inactivated, phage T3-infected E. coli, is likewise devoid of methylated bases. Such methyl-deficient T2 phage appears to be normal in its biological properties so far examined.