CHAPTER 20Polynucleotide Kinase (EC 2.7.1.78)
Martin J. Maunders
- Introduction
The enzyme polynucleotide kinase (PNK, or ATP:5'-dephospho-
polynucleotide 5'-phosphatase) catalyzes the transfer of a T-phosphate
group from a 5'-nucleoside triphosphate moiety to a free 5'-hydroxyl
ofa polynucleotide such as DNA or RNA, to form a 5'-phosphorylated
DNA or RNA molecule and a nucleoside diphosphate.
This activity has been identified in E. coli infected with bacterio-
phages T2, T4, or T6 (1,2). No enzyme can be detected in the uninfected
bacterium, but a similar kinase activity has been observed in mamma-
lian tissues, including rat liver (3,4), calf thymus (5), and various cell
lines including Chinese hamster lung cells (6) and HeLa cells (7). The
bacteriophage enzymes act on both DNA or RNA, whereas the mam-
malian enzymes are generally active only on DNA. Exceptions to this
are the calf thymus enzyme, which has a slight action on RNA, and the
HeLa cell enzyme, which is solely RNA-specific.
The in vivo role of the enzyme is possibly in maintaining DNA or
RNA in the 5'-phosphorylated, Y-hydroxylated state, which is the
substrate for many reactions such as ligation and packaging.
Polynucleotide kinase has many uses in molecular biology, however
they can be grouped into two classes. The kinasing activity can be used
purely to modify DNA, RNA, or synthetic oligonucleotides for subse-
quent manipulations, or it can enable the radiolabeling of these molecules
for subsequent detection in probing, mapping, or sequencing experiments.
From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology
Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ343