The effect of different divalent cations on the kinetics and fidelity of Bacillus stearothermophilus DNA polymerase

Although Mg(2+) is the metal ion that functions as the cofactor for DNA polymerases (DNA pols) in vivo, Mn(2+) can also serve in this capacity but it reduces base discrimination. Metal ions aside from Mg(2+) or Mn(2+) 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 Mg(2+) or Mn(2+) 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 Co(2+) and Cd(2+) were the only cations tested that could replace Mg(2+) or Mn(2+). When Co(2+) was substituted for Mg(2+), the incorporation efficiency for correct dNTPs increased 6-fold but for incorrect dNTPs there was a decrease which depended on the incoming dNTP. With Mn(2+), base selectivity was impaired compared to Co(2+) and Cd(2+). In addition, Co(2+) and Mn(2+) helped BST pol to catalyze primer-extension past a mismatch. Finally both Co(2+) and Mn(2+) enhanced ground-state binding of both correct and incorrect dNTPs to BST pol: Dideoxy terminated primer-template complexes.