Display of somatostatin-related peptides in the complementarity determining regions of an antibody light chain

Protein-protein interactions and selection: generation of molecule-binding proteins on the basis of tertiary structural information

Antibodies and their fragments are attractive binding proteins because their high binding strength is generated by several hypervariable loop regions, and because high-quality libraries can be prepared from the vast gene clusters expressed by mammalian lymphocytes. Recent explorations of new genome sequences and protein structures have revealed various small, nonantibody scaffold proteins. Accurate structural descriptions of protein-protein interactions based on X-ray and NMR analyses allow us to generate binding proteins by using grafting and library techniques. Here, we review approaches for generating binding proteins from small scaffold proteins on the basis of tertiary structural information. Identification of binding sites from visualized tertiary structures supports the transfer of function by peptide grafting. The local library approach is advantageous as a go-between technique for grafted foreign peptide sequences and small scaffold proteins. The identification of binding sites also supports the construction of efficient libraries with a low probability of denatured variants, and, in combination with the design for library diversity, opens the way to increasing library density and randomized sequence lengths without decreasing density. Detailed tertiary structural analyses of protein-protein complexes allow accurate description of epitope locations to enable the design of and screening for multispecific, high-affinity proteins recognizing multiple epitopes in target molecules.

Grafting of material-binding function into antibodies Functionalization by peptide grafting

Quite recently, a few antibodies against bulk material surface have been selected from a human repertoire antibody library, and they are attracting immense interest in the bottom-up integration of nanomaterials. Here, we constructed antibody fragments with binding affinity and specificity for nonbiological inorganic material surfaces by grafting material-binding peptides into loops of the complementarity determining region (CDR) of antibodies. Loops were replaced by peptides with affinity for zinc oxide and silver material surfaces. Selection of CDR loop for replacement was critical to the functionalization of the grafted fragments; the grafting of material-binding peptide into the CDR2 loop functionalized the antibody fragments with the same affinity and selectivity as the peptides used. Structural insight on the scaffold fragment used implies that material-binding peptide should be grafted onto the most exposed CDR loop on scaffold fragment. We show that the CDR-grafting technique leads to a build-up creation of the antibody with affinity for nonbiological materials.