Figure 3.

Adaptive interactions by conserved residues to sequence variations. A, a completely conserved Ser at position −5 in each ZF interacts with DNA that differs from triplet to triplet. B, Ser⁷³² interaction with G0. C, Ser⁷⁶⁰ interaction with C4 via a water molecule. D, Ser⁷⁸⁸ hydrogen-bonds with A6. E, Ser⁸¹⁶ bridges between G9 and T10 via a water molecule. F, Ser⁸⁴⁴ interaction with G13. G, Ser⁸⁷² make a van der Waals contact with T15. H, superimposed ZF9 (cyan) and ZF10 (green). The Arg of the conserved RD dipeptide of ZF9 makes a DNA guanine base interaction (see Fig. 2E), whereas the corresponding Arg of ZF10 makes a DNA-phosphate interaction (I). I, Arg⁷⁸⁵ of the RD dipeptide of ZF10 contacts a DNA backbone phosphate group. J, superimposition of ZF9 (cyan) and ZF12 (orange). K, Arg⁸⁴¹ of the RD dipeptide of ZF12 makes a DNA phosphate interaction. L, Arg⁸⁶⁹ at the −8 position of the RN dipeptide of ZF13 interaction with a DNA phosphate group.