Fig. 2
From: A new paradigm of DNA synthesis: three-metal-ion catalysis
Comparison of the initiation of phosphoryltransfer in two- versus three-metal-ion catalysis. a In three-metal-ion catalysis, the C-site metal ion initiates the reaction by breaking the existing phosphodiester bond in dNTP and thus drives the phosphoryltransfer reaction. A well-aligned native 3′-OH is required for capture of the C-site metal ion and its deprotonation is a result of the reaction. b In two-metal-ion catalysis, the reaction starts by de-protonation of the 3′-OH (nucleophile), which activates nucleophilic attack and leads to breakage of the existing phosphodiester bond in dNTP