FIG 2.

Effects of deletions in the EGFR tail on EGFR phosphorylation. (A) The vIVb deletion in the proximal region of the EGFR tail enhances autophosphorylation on Tyr 1068 and Tyr 1173, even in the absence of EGF stimulation. The top panels represent the whole data set (A.U., arbitrary unit). Data for the wild type (WT) and deletion mutants are shown. Phosphorylation levels with EGF stimulation (+) and without EGF (−) stimulation are shown. The bar graphs in the bottom panels present the data from cells expressing intermediate levels of EGFR. Phosphorylation levels are normalized to the unstimulated, wild-type EGFR-expressing cells. (B) Same as in panel A, but showing data for cells expressing the Δ(999–1186) EGFR mutant with a deletion in the distal region of the tail. The levels of phosphorylation detected for Tyr 974 and Tyr 992 are substantially lower than those for the wild type. (C) Effects of the same deletion constructs as in panels A and B on the activation loop tyrosine (Tyr 845). The vIVb deletion in the proximal region leads to enhanced phosphorylation, whereas deletion of the distal region of the tail is necessary for activation loop tyrosine phosphorylation. Data are presented as in panels A and B.