Large Fragment of DNA Polymerase I from Geobacillus sp. 777: Cloning and Comparison with DNA Polymerases I in Practical Applications

Abstract

A truncated gene of DNA polymerase I from the thermophilic bacteria Geobacillus sp. 777 encoding a large fragment of enzyme (LF Gss pol) was cloned and sequenced. The resulting sequence is 1776-bp long and encodes a 592 aa protein with a predicted molecular mass of 69.8 kDa. Enzyme was overexpressed in E. coli, purified by metal-chelate chromatography, and biochemically characterized. The specific activity of LF Gss pol is 104,000 U/mg (one unit of enzyme was defined as the amount of enzyme that incorporated 10 nmol of dNTP into acid insoluble material in 30 min at 65 °C). The properties of LF Gss pol were compared to commercially available large fragments of DNA polymerase I from G. stearothermophilus (LF Bst pol) and Bacillus smithii (LF Bsm pol). Studied enzymes showed maximum activity at similar pH and concentrations of monovalent/divalent ions, whereas LF Gss pol and LF Bst pol were more thermostable than LF Bsm pol. LF Gss pol is more resistant to enzyme inhibitors (SYBR Green I, heparin, ethanol, urea, blood plasma) in comparison with LF Bst pol and LF Bsm pol. LF Gss pol is also suitable for loop-mediated isothermal amplification and whole genome amplification of human genomic DNA.