Figure 1.

TVB-EGF binds specifically to cell surface EGFR. (A) Aliquots of extracellular supernatants from nontransfected 293 cells (−) and transfected 293 cells expressing TVB-EGF (+) were subjected to SDS/PAGE and to immunoblotting by using an EGF-specific antibody. (B) Mouse M5 cells expressing kinase-deficient EGFR, T23 cells expressing wild-type EGFR, and B82 cells, which lack EGFR, were incubated with increasing amounts of TVB-EGF. (C) M5 cells were incubated with TVB-EGF in the presence or absence of a recombinant EGF protein. (B–C) After each of these incubations, the cells were incubated with ALV-B SU-Ig and a FITC-conjugated secondary antibody and analyzed by flow cytometry as described (20).