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. Author manuscript; available in PMC: 2018 Aug 18.
Published in final edited form as: Annu Rev Biochem. 2018 Mar 1;87:239–261. doi: 10.1146/annurev-biochem-062917-012405

Figure 2.

Figure 2

Basis for DNA polymerase fidelity. (a) Determinants of the error rates of DNA polymerases. (b) Conformational and Mg2+-mediated chemical selection in the DNA synthesis reaction. The requirement for three Mg2+ ions is universal, and conformational selection (boxed) occurs in replicative and a few repair polymerases. Mg2+A binding and conformational change can occur without one another in replicative polymerases. (c) In the DNA synthesis (finger-closed) mode, a replicative polymerase (B-family RB69 as an example, PDB: 3NCI) interacts with the DNA and nascent base pair seamlessly. In the proofreading mode (PDB: 2P5O), DNA is detached from the open finger and disordered thumb, and primer strand is partially separated from the template and migrates to the Exo active site for cleavage.