Fig. 2: Extreme membrane curvature is essential for SMP-mediated lipid transfer.

a, Schematic representation of SMP-mediated lipid transfer between curved ER-like and flat PM-like liposomes. b, Size distributions of distinctly sized ER-like donor liposomes prepared from extrusion through filters with 30 nm pores followed by DNA-brick-assisted sorting or not. Diameters of liposomes were measured from negative-staining TEM images. Average diameters are presented as mean ± SD (n = 548, 1959, 916, and 329 liposomes from left to right). c, Top, time courses of lipid transfer between distinctly sized ER-like donor liposomes and PM-like acceptor liposomes in the presence of SMP at 37 °C as assessed by dequenching of NBD-PE fluorescence. Bottom left, quantifications of NBD fluorescence after incubation for 15 min or 30 min. Bottom right, initial transfer rates. Data are presented as mean ± SD (n = 3 independent experiments). ns, not significant; * P < 0.05, **P < 0.01, ****P < 0.0001 by two-way ANOVA with Bonferroni’s multiple comparisons test (bottom left) or by one-way ANOVA with Bonferroni’s multiple comparisons test (bottom right). P values: 6.4 × 10 ⁻³ (bottom left, 15 min), 5.3 × 10⁻⁵ (bottom left, 30 min), and 0.030 (bottom right) for [(SMP + 30-nm extruded ER-like liposomes) vs (SMP + 50-nm sorted ER-like liposomes)]; 2.6 × 10⁻¹⁰ (bottom left, 15 min), 1.5 × 10⁻¹² (bottom left, 30 min), and 1.3 × 10⁻⁵ (bottom right) for [(SMP + 30-nm extruded ER-like liposomes) vs (SMP + 40-nm sorted ER-like liposomes)]; 2.0 × 10⁻⁸ (bottom left, 15 min), 3.0 × 10⁻¹⁰ (bottom left, 30 min), and 2.3 × 10⁻⁴ (bottom right) for [(SMP + 50-nm sorted ER-like liposomes) vs (SMP + 40-nm sorted ER-like liposomes)]. d, Time courses of the tethering of distinctly sized ER-like donor liposomes and PM-like acceptor liposomes in the presence of SMP at 37 °C as assessed by an increase in turbidity (OD at 405 nm). Data are presented as mean ± SD (n = 3 independent experiments). Source data are provided as a Source Data file.