Fig. 3.

TGF-β-induced TβRII dimerization. (A) Distribution of the fluorescence intensity of diffraction-limited TβRII-GFP spots (n = 254) from the living cell imaging. After transfected with TβRII-GFP for 3.5 h, HeLa cells were treated with 200 pM TGF-β1 for 15 min at 4 °C before TIRFM imaging. The solid curves show the fitting of Gaussian function and the two peaks represented TβRII-GFP monomers and dimers, respectively. Correlation coefficient of the Gaussian fitting is 0.999. The arrowheads indicate the peak positions of the fitting curves. Numbers in the parentheses are the percentage of the fractions. (B) Two representative time courses of GFP emission after background correction show two-step bleaching. (C) Frequency of one-step and multistep bleaching events for TβRII-GFP (n = 252) in fixed HeLa cells.