Insertion of the T3 DNA polymerase thioredoxin binding domain enhances the processivity and fidelity of Taq DNA polymerase.

Insertion of the T3 DNA polymerase thioredoxin binding domain (TBD) into the distantly related thermostable Taq DNA polymerase at an analogous position in the thumb domain, converts the Taq DNA polymerase from a low processive to a highly processive enzyme. Processivity is dependent on the presence of thioredoxin. The enhancement in processivity is 20-50-fold when compared with the wild-type Taq DNA polymerase or to the recombinant polymerase in the absence of thioredoxin. The recombinant Taq DNA pol/TBD is thermostable, PCR competent and able to copy repetitive deoxynucleotide sequences six to seven times more faithfully than Taq DNA polymerase and makes 2-3-fold fewer AT-->GC transition mutations.