Phosphorylation of nucleic acid by an enzyme from T4 bacteriophage-infected Escherichia coli.

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Abstract
Infection of E. coli by T4 phage results in the formation of polynucleotide kinase which catalyzes the transfer of orthophosphate from adenosine triphosphate [ATP] to the 5[image]-hydroxyl termini of a wide variety of nucleic-acid compounds. The specificity of the enzyme permits the phosphorylation of deoxyribonucleic acid [DNA], ribonucleic acid [RNA], small oligonucleotides and nucleoside 3[image]-monophosphates. The natural occurrence and the number of 5[image]-hydroxyl end groups can be determined and the terminal nucleotides isolated and identified. An examination of the initial sites of hydrolysis by various endonucleases provides a sensitive assay for enzymes which hydrolyze phosphodiester bonds to an extent where acid-soluble products are not produced. The well-established metabolic pathways involving other kinases lead to the synthesis of nucleoside-5[image]-triphosphates. Whether polynucleotide kinase, together with other enzymes, might lead to the synthesis of a polynucleotide chain bearing an activated 5[image]-terminus which could result in the condensation of preformed polynucleotide chains should be investigated.The presence of 5[image]-phosphoryl termini may prevent the initiation of hydrolysis by exonucleases. The presence of 3[image]-phosphoryl end groups in DNA prevents exonuclease attack effectively and eliminates their template activity for DNA polymerase.