Binding to protein targets of peptidic leads discovered by phage display: crystal structures of streptavidin-bound linear and cyclic peptide ligands containing the HPQ sequence

The binding interactions of streptavidin with linear and cyclic peptides incorporate direct H-bonds, hydrophobic interactions and H-bonds due to water molecules. The linear and disulfide-bridged cyclic peptides have a conserved tripeptide sequence, HPQ. Cyclic peptides containing HPQ bind to streptavidin with a higher affinity. A screening of phage libraries followed by chemical preparation of sequences indicates that a structural-based design can be used along with a chemical process for the design and development of drugs.