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

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