Figure 6.

Metal coordination of polymerase-Fm7dG:dCTP* ternary structures. (A) Coordination of the catalytic and nucleotide-binding metal ions in the polη-Fm7dG:dCTP* structure. The distance between the 3′-OH of the primer terminus and the P_α of dCTP* is indicated as a double-headed arrow. The coordination of metal ions is indicated as dashed lines. Note that the 3′-OH is optimally positioned for nucleotidyl transfer. (B) Metal coordination in the published polβ-Fm7dG:dCTP* ternary complex structure (PDB CODE: 4O5K). The primer terminus 3′-OH is not coordinated to the catalytic metal ion, 4.8 Å away from the P_α of dCTP*, and poorly positioned for in-line nucleophilic attack.