Phage display of peptides and proteins is a versatile and promising to
ol for protein engineering and drug discovery programs because of the
vast libraries of sequences that can be rapidly screened for biologica
l function. Over the past year, reports have appeared in which these l
ibraries have been used to investigate the binding properties of a var
iety of receptors. Several functional protein domains have also been d
isplayed. A novel selection scheme using both protein and peptide disp
lay has been devised for determining protease cleavage specificity.