The origin of purine and pyrimidine deoxyribose in T6r+ bacteriophage.

Lanning and Cohen (1) reported that when Escherichia coli strain B is infected with T6r+ bacteriophage in a medium containing glucose-1-Cr4, the deoxyribose from the deoxyribonucleic acid of the T6rf particles liberated on lysis of the cells contains 40 to 60 per cent of the specific activity of the exogenous glucose. In parallel experiments, it was shown that the deoxyribose from the deoxyribonucleic acid of growing, uninfected cells contains only 20 to 30 per cent of the specific activity of the exogenous glucose-1-Cr4. Thus, the infection process, which calls for an increased rate of deoxyribose synthesis, also results in a shift of pathways used for deoxyribose formation from glucose. However, it remained to be shown whether this shift is true of all T6r+ deoxyribose or of only some of the T6r+ deoxyribose. It is of interest to know, for example, whether pyrimidine deoxyribose is made by a different pathway from purine deoxyribose. Experiments performed to decide this point are described in this paper. Cells grown in CY-glucose were infected with T6rf particles in media containing glucose-l-Cl4 as sole carbon source. The T6r+ DNA produced under these conditions was isolated and hydrolyzed to the deoxyribonucleoside level. The specific activity of the deoxyribose moieties of each of the four deoxyribonucleosides was then determined. Another aspect of deoxyribose synthesis concerns the nature of the deoxyribose precursor. There is much evidence to suggest that this is a ribose compound, i.e. that adenosine 5’-phosphate is the precursor of deoxyadenosine S/-phosphate. This hypothesis was tested in a series of experiments reported in this paper. Lastly, this paper also describes the characterization of a new compound isolated uniquely from enzymatic hydrolysates of T6r+ deoxyribonucleic acid, namely, &hydroxymethyl-(0-diglucosyl)-cytosine deoxyribonucleoside. Before these experiments were performed, some aspects of the chemistry and metabolism of T6r+ deoxyribonucleic acid had to be considered. First, TBr+ deoxyribonucleic acid contains the base, hydroxymethylcytosine, instead of cytosine (2). Moreover, most of this hydroxymethylcytosine is glucosylated, i.e. it has attached to its hydroxymethyl group glucosyl moieties (3). When T6r+ deoxyribonucleic acid is hydrolyzed to the nucleotide level, small amounts of hydroxymethylcytosine