Fig. 1.

Neutralization of basic residues in the EGFR juxtamembrane domain (JD) abolishes binding to PIP₂. a Alignment of the JD domains of several RTKs reveals the highly basic nature of these domains. b The sensorgrams shown were obtained by application (on/off times indicated by the arrows) of the respective peptides on the surface of a Biacore streptavidin-coated sensor chip, where a C6, biotinylated PIP₂ had been immobilized. Upper panel EGFR_645-662, middle panel EGFR_645–662MUT, lower panel a peptide derived from residues 1156–1172 of the distal C-terminus of the EGFR (EGFR_1156-1172) lacking clusters of positively charged residues. Sensorgrams are representative of multiple trials on three different sensor chips, with identical results. Peptide concentrations were (nM): for EGFR_645-672 4,000, 2,000, 1,000, 500, and 250, for EGFR_645–672MUT 500, 250, 125, 62.5, and 31.125, for EGFR_1156-1172 2,000, 1,000, 500, 250, and 125. Sensorgrams obtained from EGFR_645-672 were fitted using a 1:1 Langmuir binding model (not shown), and after subtraction from data obtained simultaneously from another channel of the same sensor chip, where no ligand had been immobilized. The data from EGFR_1156-1172 and EGFR_645–672MUT could not be fitted. At concentrations exceeding 1,000 nM, the EGFR_645–672MUT associated with the chip nonspecifically (not shown)