Directed Evolution of Bone Associated Protein Through Phage Display
University of California, Berkeley, US
phage display hydroxyapatite
The formation of natural bone is thought to occur by the templated mineralization of HA by the surrounding proteins, which include collagen and highly acidic phosphoproteins attached to the collagen scaffold. It has been proposed that the acidic groups serve as binding sites for calcium ions and align them in an orientation that matches the HA crystal lattice, but the biological mineralization process is not understood at the molecular level. Using directed evolution process of combinatorial peptide libraries, we identified specific binding peptides for single crystal hydroxyapatite in various pH ranges and study their interactions between HA binding peptides and crystal surfaces. Remarkably, the consensus HA binding peptides resulted in characteristic tripeptide repeat (Pro-X-Y) at pH 7.5 and (Ser-Ser-Asp) at pH 5. These sequences are similar to the major repeats of type I collagen and dentin phosphoproteins respectively. Using a panel of synthetic peptides, we defined the structural features required for binding and mineralizing activity of HA. We also incorporated these short HA-binding peptides to construct three-dimensional bone-like materials by designing nanofibers and responsive functional protein gels.
Nanotech 2008 Conference Program Abstract