Fig. 1.
Two regimes for amphiphysin 1 binding to a GUV membrane DOPC∶DOPE∶DOPS (1∶1∶1). (A) Adsorption isotherm of amphiphysin 1 on GUV. The amphiphysin density, Φν, deduced from the fluorescence signal, as a function of the protein bulk density Cbulk. Data are fitted with Φv = Φmax/(1 + Kd/Cbulk) with Φmax = 3,000 μm-2 and Kd = 35 nm (error bars correspond to standard deviation. N = 6 vesicles for each point). (B) For Cbulk < Kd, the amphiphysin signal (green) is undetectable on the GUV, the fluorescent lipid signal is in red, and amphiphysin is visible on the tube. (C) At high Cbulk (here equal to 1 μM) amphiphysin binds to the GUV and forms tubes rich in amphiphysin (green fluorescence). (Scale bar: 5 μm.)