Fig. 6. Detailed views of the Zn(II)-binding sites at the coiled coil interfaces that facilitate crystal packing are depicted. (A) Dinuclear Zn(II) site with a bridging glutamate residue. The Zn(II) ions are coordinated tetrahedrally by histidine and glutamate residues of three different coiled coils and one water molecule. (B) A second set of Zn(II) ions 4.7 Å apart coordinated by glutamate and histidine residues from two different coiled coils and two water molecules.

Fig. 7. A helical wheel diagram looking from the C to the N terminus of the three helices of the coiled coil, denoted A, B, and C, shows the electrostatic interactions between side chain residues. The a-g notation of the residues and the heptad repeat is shown. Electrostatic interactions between e and g residues are shown as well as one interaction between b and g residues involving Glu 24 A and Lys 22 B. Key water molecules that mediate interactions are also shown.