Isolation of specific binding peptides for ionic species of nickel and cobalt using the phage surface display technique

Since several years, the phage surface display technique has been successfully applied for the development of new receptor-ligand pairs for medical purposes, new pharmaceuticals or the elucidation of protein-protein interactions. A comparatively new methodological approach is the use of this technique for bioremediation. In the BMBF-funded German-French project "EcoMetals" we focused on novel innovative biological methods for the extraction of copper and accompanying elements from complex copper-containing ores or tailings. The selective separation of individual industrially relevant chemical elements from complex copper-containing leaching solutions represents a particular challenge. Where established chemical methods do not work due to low concentrations or complex composition of these solutions, selectively binding biological structures could become attractive. Up to now, metal-binding peptides are regarded as particularly promising candidates. We used for the isolation and characterization of nickel- and cobalt-specific peptides a bacteriophage library (Ph.D.C7C Phage Display Peptide Library Kit, New England Biolabs, Inc.) for targeted removal and enrichment of these elements from a complex leaching solution. In this library the minor coat protein pIII is genetically modified leading to the expression of 5 copies phage tail protein containing a foreign heptapeptide loop flanked by a disulfide bridge. From a pool of 109 different peptide motifs, 24 peptides for nickel and 19 peptides for cobalt were isolated in an iterative process, the so-called bio-panning. The binding strength of these phages was compared with the wildtype. Cross binding tests revealed for most of the nickel binding phages also binding capacities for cobalt and vice versa.