Fig. 1. Binding of FGF1 to cell-surface FGFRs. (A) HeLa cells, not transfected (-) or transiently transfected with FGFR1, 2, 3 or 4 were treated with Cy3-labelled FGF1 and 50 U/ml heparin for 2 hours at 4°C. The cells were then fixed and examined by confocal microscopy. The red channel image was superimposed onto the corresponding interference contrast image. Bar, 5 µm. (B) HeLa cells not transfected (-) or transiently transfected with FGFR1, 2, 3 or 4 (R1, R2, R3, R4, respectively) were incubated at 37°C with [³⁵S]methionine-labelled FGF1 and 50 U/ml heparin for 1 hour. The cells were washed with PBS and lysed. FGF1 was extracted from the lysate by binding to heparin-Sepharose and analysed by SDS-PAGE.