SELECTION OF TARGETED BIOLOGICAL MODIFIERS FROM A BACTERIOPHAGE LIBRARY OF RANDOM PEPTIDES - THE IDENTIFICATION OF NOVEL CALMODULIN REGULATORY PEPTIDES

The interaction of short amino acid sequences is the basis of molecula r recognition and biological regulation in many cellular systems. Libr aries of random peptides provide an approach to identify peptides that can be used to modulate, in a targeted fashion, the function of speci fic gene products. We have used a library of random peptides designed and constructed in the M13 bacteriophage to select calcium-dependent c almodulin binding-peptides. Twenty-eight independent sequences were ob tained; all contained a tryptophan within the fifteen-amino acid inser t. In 11 sequences, the tryptophan was located in the first possible v ariable position of the inserted sequence and was followed by a prolin e. The tryptophan-proline combination was also present in six addition al isolates but at various other positions within the peptide insert. Synthetic peptides, representative of the calmodulin binding sequences , bound to calmodulin in a calcium-dependent fashion, competed with kn own calmodulin inhibitors and, when introduced via a patch pipette, in hibited calcium-activated chloride conductance of the colonic epitheli al cell line, T84. This report demonstrates the utility of identifying modifiers of biological function and should prove to be a valuable ap proach in understanding the cellular role of proteins of unknown funct ion.