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. The exonuclease activity appears to be responsible for the high fidelity of this enzyme and prevents strand displacement synthesis
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 but is not recommended for DNA sequencing applications.
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