On the Metabolic Role of T6 Phage-induced Dihydrofolate Reductase
INTRACELLULAR REDUCED PYRIDINE NUCLEOTIDES
Christopher K. Mathews 1
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1 From the Department of Biology, Yale University, New Haven, Connecticut 06520
Infection of Escherichia coli with T-even bacteriophage or T5 leads to the production of large amounts of dihydrofolate reductase. As shown previously, this represents the synthesis of a new, virus-specific protein. Since appreciable levels of this enzyme exist in the cell before infection, an attempt was made to demonstrate a specific metabolic requirement for the viral enzyme. This included (a) a study of the structure of tetrahydrofolate produced enzymatically by both the bacterial and the viral reductase and (b) measurements of levels of reduced pyridine nucleotides in the cell before and after infection. Both the cellular and the phage-specific reductase catalyze the formation of the l, l diastereoisomer of tetrahydrofolate, as does the same enzyme isolated from chicken liver. Experiments on pyridine nucleotide concentrations reveal a 2- to 3-fold increase in the reduced forms of both di- and triphosphopyridine nucleotide occurring within about 10 min after infection, followed by a return to preinfection values. These observations are discussed with reference to the reductive biosynthetic steps in the production of deoxyribonucleic acid.
Submitted on June 2, 1966
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