Recombinant His-tagged DNA polymerase. I. Cloning, purification and partial characterization of Thermus thermophilus recombinant DNA polymerase.

The Tth DNA polymerase gene from the thermophilic Thermus thermophilus (strain HB8) was amplified, cloned and expressed in Escherichia coli. The recombinant DNA polymerase containing a polyhistidine tag at the N-terminus was isolated in a single step by Ni2+ affinity chromatography. The purified recombinant enzyme, showing high polymerase activity contained 43 additional amino-acid residues (including a cluster of six histidine residues inserted for purification of the recombinant protein by metal-affinity chromatography) at N-terminus. The applied overexpression system was very efficient giving 700,000 u of DNA polymerase activity from 1 liter of induced culture. The enzyme was characterized and displayed high DNA polymerase and reverse transcriptase activities and high thermostability as compared to the native Tth DNA polymerase.