Temperature dependence of accuracy of DNA polymerase I from Geobacillus anatolicus.

Klenow-like DNA polymerase I fragment from Geobacillus anatolicus (GF) was cloned and purified. The accuracy of GF was measured in vitro at three different temperatures under single turnover conditions as well as using a forward mutation assay. In pre-steady-state kinetic measurements, when temperature was raised from 22 °C to 50 °C, the rate (k(pol)) for cognate dTTP and non-cognate dATP nucleotide incorporations increased six- and four-fold, respectively, whereas the K(d) for both nucleotide incorporations changed only slightly. As a result, the error frequency was remained constant (∼4 × 10(-4)) over this temperature range. The accuracy of GF was also measured using a forward mutation assay during a single cycle of DNA synthesis of the lacZα complementation gene in M13mp2 DNA. In this assay, which scores various types of replication errors, mutant frequency of GF was 5 × 10(-3) at 72 °C which is four-fold higher than that of 37 °C.