Using GST-Src SH3 fusion protein to screen the phage-displayed RPLs T914 and T1218, is we have isolated biologically active peptide ligands for, and characterized the binding specificity of, the Src SH3 domain.9 Peptides displayed by Src SH3 affinity-purified phage contain similar proline-rich regions that yield a consensus motif of RPLPPLP (Fig. 3); this motif is similar to a region of p85 phosphatidylinositol 3'-kinase known to interact with Src SH3.5,8 Phage expressing peptides related to the RPLPPLP motif bind GST-Src SH3, but not GST-Abl SH3 or GST alone (Fig. 4). Similarly, synthetic peptides containing the RPLPPLP motif compete Src SH3-binding proteins, but not Abl SH3- or PLCγSH3-binding proteins, from cell lysates.9 Finally, RPLPPLP-related peptides are able to accelerate progesteroneinduced maturation of Xenopus laevis oocytes9; a similar acceleration is observed in oocytes treated with activated, but not normal, Xenopus Src.27 These results suggest that screening nonbiased peptide libraries may represent a general means of isolating peptide ligands for, and characterizing the binding specificities of, other domains thought to mediate proteinprotein interactions, including other SH3 domains, armadillo repeats, and PH domains.
ASJC Scopus subject areas
- Molecular Biology