TIGHT-BINDING INHIBITORY SEQUENCES AGAINST PP60(C-SRC) IDENTIFIED USING A RANDOM 15-AMINO-ACID PEPTIDE LIBRARY

A bacteriophage peptide library containing a random 15-amino-acid inse rt was screened for identification of peptide sequence(s) that bind pp 60(c-src). Sequencing the random insert from more than 100 virions ind icated that more than 60% of the phage virions that bound to this enzy me contained a GXXG sequence motif in which X was frequently a hydroph obic residue, The GXXG sequence was often repeated as GXXGXXG. Two non americ peptides were synthesized to determine whether or not the pepti de inhibits pp60(c-src) tyrosine kinase activity and the importance of the glycine residues within this sequence, The peptide containing gly cine had a K-i of 24 mu M, whereas replacing the glycines with proline increased the K-i value to 3.1 mM.