Selection of novel structural zinc sites from a random peptide library

Zinc ion (Zn²⁺) can be coordinated with four or three amino acid residues to stabilize a protein's structure or to form a catalytic active center. We used phage display selection of a dodecamer random peptide library with Zn²⁺ to identify structural zinc sites. The binding specificity for Zn²⁺ of selected sequences was confirmed using enzyme-linked immunosorbent and competitive inhibition assays. Circular dichroism spectra indicated that the interaction with Zn²⁺ induced a change in conformation, which means the peptide acts as a structural zinc site. Furthermore, a search of protein databases revealed that two selected sequences corresponded to parts of natural zinc sites of copper/zinc superoxide dismutase and zinc-containing ferredoxin. We demonstrated that Zn²⁺-binding sequences selected from the random combinatorial library would be candidates for artificial structural zinc sites.