High affinity binding of an N-terminal myristoylated p60src peptide

N-Myristoyl and non-myristoyl peptides corresponding to the N terminus of p60src were used to examine whether N-myristoylation facilitates the binding of p60src to specific protein sites at the plasma membrane. We discovered high affinity protein acceptor sites (Kd = 2.7 nM) to a 15-amino acid N-myristoylated N-terminal p60src peptide in red cell membrane vesicles. Binding was not competed by the non-myristoylated analog of the peptide nor by shorter N-myristoyl src peptides and peptides homologous to the N terminus of other N-myristoylated proteins. Binding was not evident after treatment of vesicles with proteolytic enzymes. Raising the salt concentration of the buffer to 50 mM NaCl caused an apparent inhibition of binding. However, no significant effect of salt was observed on the off-rate of bound ligand under these conditions. The results indicate the existence of N-myristoyl-dependent p60src protein acceptor sites at or near the plasma membrane/skeleton interface of red cells which could be responsible for the localization of p60src to this region and may represent new regulatory components for p60src-mediated tyrosine kinase activity.