Metal-binding Peptides: Displaying And Screening On Microorganism, And Its Application In Bioadsorption

Many heavy metals have constituted a global environment hazard. Bioremediation would clean up the metal contamination efficiently and ecologically. Recent research has focused on how to obtain the metal-binding peptides( MBPs) with higher affinity and selectivity.In the research, biopanning was carried out against Ni-NTA HisSorb strips. At first, nickel-binding peptides were selected both from phage-displayed random constrained heptapeptide library and linear random dodepeptide library, most of the peptides contain the sequence "HHHH". When displayed on the bacterial surface, the selected peptides improved the Ni-binding capacity of recombinant bacteria. Then FliTrx displayed peptide library was directly screened against the strips, and the isolated bacterial clones displayed peptides with no conserved sequence but high content of histidines.On the base of the MBP sequences from the screening of peptide libraries and the primary bacterial peptide library, two histidine-biased peptide libraries, that is the second- generation library (SGL), was designed and constructed. SGL1 is the library with insert "XXHHXXX", SGL2 with "XXHXHXX". After biopanning, many of the isolated bacterial clones from the two SGL contained the common sequence "HHH", and Arg residue was often found flanking His. Two of the selected clones, displaying "RNHHNSW" and "LRHRHRR" repectively, exhibited stronger Ni-immobilized binding capacity than the clone with polyhistidine insert.The biopanning method with Ni-immobilized micro-well was established primarily. Flagellin was utilized as the anchor protein to display MBPs for the first time. Thestrategy to optimize MBPs by screening the biased peptide library was explored, and seemed promising. The study would throw light on the relationship between the structure and function of MBP, also on the microorganism bioadsorption.