T7 DNA polymerase

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The T7 DNA polymerase of the T7 bacteriophage is a DNA-dependent DNA polymerase responsible for the fast rate of T7 phage DNA replication in vivo. The polymerase consists of a 1:1 complex of the viral T7 gene 5 protein (80kDA) and the E. coli thioredoxin (12kDA).

It lacks a 5'→ 3' exonuclease domain, but the 3'→5' exonuclease activities are approximately 1000-fold greater than that of Klenow fragment.[1] The exonuclease activity appears to be responsible for the high fidelity of this enzyme and prevents strand displacement synthesis [2]

This polymerase is unique due to its considerable processivity, or ability to stay on DNA for a greater than average number of base pairs. It is also suitable for site-directed mutagenesis [3] but is not recommended for DNA sequencing applications.[4]


  1. ^ Sambrook, J., Russell, D.W. (2001). "Molecular Cloning: A Laboratory Manual, Third edition". Cold Spring Harbor Laboratory Press (Cold Spring Harbor, New York, 2001.). 
  2. ^ LECHNER, R. L. AND RICHARDSON, C. C. (1983). "A preformed, topologically stable replication fork.". J. Biol. Chem. 258 (18): 11185–11196. PMID 6885816. 
  3. ^ BEBENEK, K. et al. (1989). "The use of native T7 DNA polymerase for site-directed mutagenesis.". Nucl. Acids Res. 17 (13): 5408. doi:10.1093/nar/17.13.5408. PMC 318147. PMID 2668888. 
  4. ^ Doublie S., Tabor S., Long A., Richardson C., and Ellenberger T. (1998). "Crystal Structure of a Bacteriophage T7 DNA Replication complex at 2.2 A Resolution.". Nature 391 (6664): 251–258. doi:10.1038/34593. PMID 9440688.