DNA Polymerase I from Acinetobacter calcoaceticus: Enzymatic Properties

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Abstract
Certain enzymatic properties of homogenous DNA polymerase I from Acinetobacter calcoaceticus have been investigated. The enzyme requires an initiator DNA for normal DNA repair synthesis. It is, however, also capable of de novo synthesis in the presence of dATP and dTTP or dGTP and dCTP. The enzyme was only partially inhibited by the–SH‐group‐blocking reagent p‐hydroxymercuribenzoate.DNA polymerase I from Acinetobacter calcoaceticus contained both a 3′→ 5′ and a 5′→ 3′ exonuclease activity. The products of the former was 5′‐deoxymononucleotide phosphates. The 5′→ 3′ nuclease gave mononucleotides with T7 DNA and with d(A‐T)n the products were mono, di, and trinucleotides, the ratio depending on the concentration of Mg2+· The 3′→ 5′ exonuclease activity appeared to be slightly more active on single‐stranded than double‐stranded DNA. The opposite was the case for the 5′→ 3′ nuclease which had an absolute requirement for double‐stranded DNA. The present work offers further evidence for the view that DNA polymerase I enzymes in microorganisms have similar structural features and enzymatic properties.