Phage display scaffolds

The innovative potential and the ingenuity which have gone into designing libraries, vectors and selection protocols are impressive. However, considerable input has come from structural modelling and design considerations, in the proliferation of phage-display scaffolds to provide constrained variable epitopes in different environments or contexts . In addition the method has been used to understand protein folding, protein-protein interactions and structure-function relationships in catalysis. I hope that, in this review,... 

EMPl, selected by phage display from random peptide libraries, demonstrates that a dimer of a 20-residue peptide can mimic the function of a monomeric 166-residue protein. In contrast to the minimized Z domain, this selected peptide shares neither the sequence nor the structure of the natural hormone. Thus, there can be a number of ways to solve a molecular recognition problem, and combinatorial methods such as phage display allow us to sort through a multitude of structural scaffolds to discover novel solutions. 

Structural scaffolds can be reduced in size while function is retained Phage display of random peptide librciries... 

Antibody fragment libraries from immunized and nonimmunized sources can be used in phage display and peptide libraries are commercially available. An alternative technique is to design protein aptamers that consist of a stable protein scaffold on which random peptides are displayed. An example of protein aptamers are affibodies, which present a library of 13 randomized amino acids on the Z domain of Staphylococcus aureus protein A. Crystal structure studies indicate similarity in the binding of an affibody to its target to protein-antibody interactions. However, affibodies have a dissociation constant of approximately 1 /.tM compared to antibody-antigen complexes ofl nM orless(H3, Rl, Wl). 

In analogy with constrained peptide libraries, several reports have described the use of small proteins, protein domains, or antibodies as scaffolds for the display of random polypeptide sequences to obtain novel binding proteins or antibodies. Koide et al. (81) used the tenth FN3 sequence, a 94-amino-acid fibronectin domain (82, 83) known to be involved in molecular recognition, as a scaffold to build a phagemid 3+3 library L7 (Fig. 10.16) where less than a copy of modified FN3 was present on each phage capsid. The 10 -member library was screened using plates coated with ubiquitin, a small protein for which native FN3 does not have any affinity. The library was made by randomizing five amino acids in positions 26-30 (BC) and five amino acids in... 

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