Nucleotides derived from enzymatic digests of nucleic acids of T2, T4, and T6 bacteriophages.

The compositions of the nucleic acids of the T even bacteriophages, T2, T4, and T6 have been shown to be identical with respect to their purine and pyrimidine bases within the accuracy of existing analytical methods for these bases (1). However these viruses contain the unusual pyrimidine, 5-hydroxymethyl cytosine, which provides a unique opportunity for chemical variability in the composition of these nucleic acids. Cohen found (2) that enzymatic digestion of phage nucleic acids by pancreatic deoxyribonuclease and intestinal phosphatase released large amounts of the deoxyribonucleosides of adenine, guanine, and thymine but only a very small proportion of the HMCY deoxyribonucleoside, although a similar digestion of thymus deoxyribonucleic acid leads to a quantitative degradation to the deoxyribonucleosides. It was suggested that the structural relations of HMC in some way conferred resistance to the phosphoesterase action of these enzymes. The HMC deoxyribonucleoside was released by phosphatase after a preliminary acid hydrolysis (2). It was reported in 1946 that purified preparations of T2r+ bacteriophage contained hexose which reacted like glucose (3). Jesaitis and Goebel (4) have reported on the presence of hexose in T4 preparations and Jesaitis (5) first demonstrated the association of glucose with the viral nucleic acid. In 1954 Volkin (6) and Sinsheimer (7) showed independently that the DNA’s of T4r and T2r+ bacteriophages, respectively, could be hydrolyzed, albeit incompletely, by pancreatic DNase and by venom phosphodiesterase to liberate small amounts of a nucleotide which contained both HMC and glucose. The glucose was present as an 0-glycoside of the 5-hydroxymethyl substituent on the pyrimidine. In the digests of T4r+ nucleic acid the ratio of glucose to HMC in various fractions was 1: 1 (6). However, two HMC nucleotides were isolated by ion exchange chromatography from digests of T2r+ DNA, one of which contained a mole of glucose per mole of HMC whereas the other was free of the hexose (7). It was reported that the monoglucosyl HMC nucleotide is dephosphorylated by a 5’-nucleotidase at a markedly slower rate than is the nonglucosylated dHMP (7). Jesaitis (8) has analyzed the DNA of wild type r+ strains of T2, T4, and T6 and has shown that the three strains, which contain essentially similar amounts of HMC, contain different amounts of glucose in the amount of approximately 0.8, 1.0,