ANALYSIS OF NOVEL STREPTAVIDIN-BINDING PEPTIDES, IDENTIFIED USING A PHAGE DISPLAY LIBRARY, SHOWS THAT AMINO-ACIDS EXTERNAL TO A PERFECTLY CONSERVED CONSENSUS SEQUENCE AND TO THE PRESENTED PEPTIDES CONTRIBUTE TO BINDING

Streptavidin-binding peptides containing the consensus amino acid sequ ence motif EPDW were identified using a phage display library. Phage p resenting peptides containing these sequences bound streptavidin in a biotin-sensitive fashion and could be eluted with biotin. The previous ly identified 'streptag' peptide sequence (AWRHPQGG) competed with pha ge presenting the EPDW consensus sequence for streptavidin binding. Fu rthermore, the EPDW sequence has two amino acids in common with yet an other previously identified streptavidin-binding sequence, GDWVFI, whi ch has similar biochemical properties. Binding inhibition studies reve aled that residues flanking EPDW, as well as residues of the modified phage pIII product to which displayed peptides are fused, contributed to streptavidin binding. The derivation of small molecules based on th e structure of peptides selected using display methods is a potentiall y important application of phage display technology. The relevance of the observations made here for that application are discussed. Finally a group of 'nuisance' peptides of the consensus sequence WHWWXW, whos e binding specificity has not been fully elucidated, but which have be en isolated in a number of biopanning experiments, including those tha t do not utilize streptavidin, are also described.