Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1983 Nov 25;258(22):14017-24.

The gene 4 protein of bacteriophage T7. Characterization of helicase activity

S W Matson, S Tabor, C C Richardson
  • PMID: 6315716
Free article

The gene 4 protein of bacteriophage T7. Characterization of helicase activity

S W Matson et al. J Biol Chem. .
Free article

Abstract

Gene 4 protein of bacteriophage T7 is a multifunctional enzyme that both stimulates T7 DNA polymerase during leading strand synthesis, and synthesizes RNA primers that initiate lagging strand synthesis. Both activities are dependent on the ability of the gene 4 protein to translocate unidirectionally (5' to 3') along single-stranded DNA (Tabor, S., and Richardson, C.C. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 205-209), a reaction that is coupled to the hydrolysis of nucleoside 5'-triphosphates. In this paper, we show that gene 4 protein, in the absence of other proteins, is a helicase, an activity previously inferred from its ability to stimulate T7 DNA polymerase on duplex DNA. We have designed a DNA substrate for use in characterizing the helicase activity which consists of a short DNA fragment bearing a single-stranded 3'-tail when annealed to circular, single-stranded M13 DNA. With such a DNA substrate, the gene 4 protein can disrupt the helical structure of a 96-nucleotide-long fragment, resulting in its displacement from the circle. Helicase activity requires a long stretch of at least 17 nucleotides of single-stranded DNA on the 5'-side of the duplex to be unwound. In addition, helicase activity is not observed unless a short (greater than 6 nucleotides) single-stranded 3'-tail is present. The helicase activity has an absolute requirement for hydrolysis of a nucleoside 5'-triphosphate. The inhibitor of nucleoside triphosphate hydrolysis, beta, gamma-methylene dTTP, is an effective inhibitor of helicase activity. Based on these results, we propose a model for the action of the gene 4 protein at a replication fork.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types

LinkOut - more resources