Development of a selective pseudosubstrate-based peptide inhibitor of pp60 (c-src) protein tyrosine kinase

Using a combinatorial peptide library method, we identified YIYGSFK as an efficient and specific peptide substrate for pp60(c-src) protein tyrosine kinase (PTK) [Lam et al., Int, J. Pept. Protein Res., 45 (1995) 587]. Employing YIYGSFK as a template, we synthesized and evaluated a series of pseudosubstrate-based inhibitors for pp60(c-src) We found that the efficiency of a given inhibitor was highly dependent on the specific tyrosine analog used at the phosphorylation site of the substrate, One of these pseudosubstrate inhibitors, YI(2'-Nal)GSFK, selectively inhibited the kinase activity of pp60(c-src), with a K-i of 24 mu M. This peptide inhibitor exhibited selectivity for pp60(c-src) as compared to other PTKs tested, such as c-Abl and Bcr-Abl, Our results suggest that selective inhibitors for a specific PTK can be developed when the structure of a specific and efficient small peptide substrate for this PTK can be used as a template for structure modification.