Why is Zinc Important?

  First, zinc can provide a purely structural role because it has a completely filled d-orbital.  This role is exhibited by the different zinc finger motifs on the DNA-Protein Interaction page. 

 Second, Zn⁺⁺ is a "borderline" acid, which can make different types of interactions depending on the type of ligand it's associating with:

                                                                                           S (Cys)  à  Soft base

                                                                                           N (His)     à  Hard base

                                                                                           O (Glu, Asp, H₂O)  à Hard base