Novel Zn2+-chelating peptides selected from a fimbria-displayed random peptide library

The display of peptide sequences on the surface of bacteria is a technology that offers exciting applications in biotechnology and medical research. T ype 1 fimbriae are surface organelles of Escherichia coli which mediate D-m annose-sensitive binding to different host surfaces by virtue of the FimH a dhesin. FimH is a component of the fimbrial organelle that can accommodate and display a diverse range of peptide sequences on the E. coli cell surfac e. In this study we have constructed a random peptide library in FimH. The library, consisting of similar to 40 million individual clones, was screene d for peptide sequences that conferred on recombinant cells the ability to bind Zn2+. By serial selection, sequences that exhibited various degrees of binding affinity and specificity toward Zn2+ were enriched. None of the is olated sequences showed similarity to known Zn2+-binding proteins, indicati ng that completely novel Zn2+-binding peptide sequences had been isolated. By changing the protein scaffold system, we demonstrated that the Zn2+-bind ing seems to be uniquely mediated by the peptide insert and to be independe nt of the sequence of the carrier protein. These findings might be applied in the design of biomatrices for bioremediation purposes or in the developm ent of sensors for detection of heavy metals.