Deoxyribonucleic acid polymerase from the extreme thermophile Thermus aquaticus

Abstract

A stable DNA polymerase (EC 2.7.7.7) with a temperature optimum of 80.degree. C was purified from the extreme thermophile T. aquaticus. The enzyme is free from phosphomonoesterase, phosphodiesterase and single-stranded exonuclease activities. Maximal activity of the enzyme requires all 4 deoxyribonucleotides and activated calf thymus DNA. An absolute requirement for divalent cation cofactor was satisfied by Mg2+ or to a lesser extent by Mn2+. Monovalent cations at concentrations as high as 0.1 M did not show a significant inhibitory effect. The pH optimum was 8.0 in tis(hydroxymethyl)aminomethane-hydrochloride buffer. The MW of the enzyme was estimated by sucrose gradient centrifugation and gel filtrations on Sephadex G-100 to be .apprx. 63,000-68,000. The elevated temperature requirement, small size and lack of nuclease activity distinguish this polymerase from the DNA polymerases of Escherichia coli.