Figure 7.

The two orientations and resulting interactions of d(T)-AP(U)-d(T)-3′ at the wt-KF exonuclease active site. Only one of the orientations is compatible with a direct phosphate-metal ion interaction (A). However, the Zn²⁺ … 0 distance is longer (2.49 Å) compared with the hexamer complex (1.81 Å, Fig. 6A). See Fig. 6 for color scheme and further explanations.