Detection in situ of active polypeptides of mammalian and T4 DNA kinases after sodium dodecyl sulfate/polyacrylamide gel electrophoresis.

DNA kinase activity of rat liver nuclei was detected in situ after electrophoresis in sodium dodecyl sulfate/polyacrylamide gel containing 5'-hydroxyl nicked DNA as DNA substrate. After renaturation of polypeptides, the gel was incubated with [gamma-32P]ATP and Mg2+. An active polypeptide corresponding to Mr 61,000 was observed as a radioactive band by autoradiography. The intensity of the band was proportional to the amount of the enzyme applied. The active band common to various tissues of rat was observed with the nuclear extracts, indicating that DNA kinase for rat tissue is composed of a single polypeptide of Mr 61,000. In contrast, T4 polynucleotide kinase (Mr = 140,000) showed an active polypeptide band corresponding to the subunit of Mr 33,000.