The Effect of Different Divalent Cations on the Kinetics and Fidelity of Bacillus Stearothermophilus DNA Polymerase.

Although Mg2+ is the metal ion that functions as the cofactor for DNA polymerases (DNA pols) in vivo, Mn2+ can also serve in this capacity but it reduces base discrimination. Metal ions aside from Mg2+ or Mn2+ can act as cofactors for some DNA pols but not for others. Here we report on the ability of several divalent metal ions to substitute for Mg2+ or Mn2+ with BST DNA polymerase (BST pol), an A family DNA pol. We selected the metal ions based on whether they had previously been shown to be effective with other DNA pols. We found that Co2+ and Cd2+ were the only cations tested that could replace Mg2+ or Mn2+. When Co2+ was substituted for Mg2+, the incorporation efficiency for correct dNTPs increased 6-fold but for incorrect dNTPs there was a decrease which depended on the incoming dNTP. With Mn2+, base selectivity was impaired compared to Co2+ and Cd2+. In addition, Co2+ and Mn2+ helped BST pol to catalyze primer-extension past a mismatch. Finally both Co2+ and Mn2+ enhanced ground-state binding of both correct and incorrect dNTPs to BST pol: Dideoxy terminated primer-template complexes.