Fig. 3.

Cholera toxin B-subunit (CTxB) binding to GM1 enhances lipid sorting. (A and B) Sorting ratio for DHPE* to GM1* as a function of the reference curvature (Ref. curvature) for 0:0:100 vesicles (A) and for 30:35:35 vesicles (B) with (filled symbols) and without (open symbols) CTxB in solution. Linear fits in the presence of CTxB give (11.7 × C_r + 1) for the 0:0:100 composition and (37 × C_r + 1) for the 30:35:35 composition, with the reference curvature C_r in nm⁻¹. Data are binned over 4 points (for 0:0:100, n = 9 vesicles with CTxB and n = 10 without; for 30:35:35, n = 8 vesicles with CTxB and n = 12 without; error bars represent the standard error of the mean). The horizontal line (sorting = 1), a guide to the eye, corresponds to the absence of sorting. (C) Effect of CTxB binding on the tube force. The force is plotted as f/$\sqrt{\sigma }$ vs. σ following Eq. 4. Data for the 30:35:35 membranes are binned over 4 points (n = 8 vesicles with CTxB and n = 12 without; error bars represent the standard error of the mean). Linear fits give: (−8.3 × 10⁻⁶ × σ + 3.4 × 10⁻⁹) and (−4.5 × 10⁻⁶ × σ + 3.3 × 10⁻⁹) for the 30:35:35 composition with and without CTxB, respectively.