FIGURE 5.

Y253D-ErbB2 does not modulate EGF receptor binding affinity. Cells constitutively expressing the EGF receptor were stably transfected with wild type ErbB2 (panel A), K732M-ErbB2 (panel B), or Y253D-ErbB2 (panel C) expressed from a tet-inducible promoter. For assay, cells were grown in the absence (open circles) or presence (filled circles) of doxycycline to induce the expression of ErbB2. All lines express ∼300,000 EGF receptors/cell. Relative levels of ErbB2 expressed in each line are shown in the inset of panel A. ¹²⁵I-EGF binding isotherms were then generated in cells expressing only the EGF receptor or the same number of EGF receptors plus the different forms of ErbB2.