The amino acid sequence required for 5' -> 3' exonuclease activity of Bacillus caldotenax DNA polymerase

We studied the 5' 3' exonuclease activity of Bacillus caldotenaxDNA polymerase by site-directed mutagenesis. Among seven mutantsconstructed, two mutant DNA polymerases with an amino acid substitutionof Glyl84 Asp or Glyl92 Asp were confirmed to be deficientin this exonuclease. The two positions corresponded to thoseof the Escherichia coli DNA polymerase I mutants defective in5' 3' exonuclease, polA480ex and polA214. These results provideexperimental support for the proposed amino acid sequence essentialfor the 5' 3' exonuclease activity associated with eubacterialpolymerase I–like DNA polymerases (family A), includingE.coli and Thermits aquaticus.