ATP-phosphopeptide conjugates as inhibitors of Src tyrosine kinases.

A number of Src SH2 domain inhibitors enhance the kinase catalytic activity by switching the closed inactive to the open active conformation. ATP-phosphopeptide conjugates were designed and synthesized as Src tyrosine kinase inhibitors based on a tetrapeptide sequence pTyr-Glu-Glu-Ile (pYEEI) and ATP to block the SH2 domain signaling and substrate phosphorylation by ATP, respectively. In general, ATP-phosphopeptide conjugates with optimal linkers such as compounds 5 and 7 (K(i) = 1.7-2.6 microM) showed higher binding affinities to the ATP-binding site relative to the other ATP-phosphopeptide conjugates having short or long linkers, 1-4 and 6, (K(i) = 10.1-16.1 microM) and ATP (K(m) = 74 microM). These ATP-phosphopeptide conjugates may serve as novel templates for designing protein tyrosine kinase inhibitors to block SH2 mediated protein-protein interactions and to counter the activation of enzyme that resulted from the SH2 inhibition.