FIG. 1.

Composition of the NPXY/NXXY motif database and peptide synthesis. (A) Origin of all 126 NXXY motifs identified by surveying human protein sequences classified as receptors. Twenty percent of the sites were derived from RTKs, several of which contain multiple motifs. (B) Peptide arrays comprised of the entire database were synthesized on cellulose membranes. The SPOT template represents a typical synthesis composed of both unphosphorylated (black) and phosphorylated (gray) versions of each 12-mer motif. Western blotting (WB) with anti-pTyr antibodies was able to confirm its presence in most peptides. Also, selective coupling of biotin to only full-length products, with subsequent detection using avidin-HRP, demonstrated that all peptides were adequately synthesized.