Fig. 5: Transmembrane coupling of protein condensates correlates with changes in lipid organization and mobility.

a Schematic of the transmembrane coupling process. Left: Protein condensates induce local reorganization of lipids (blue lipid heads). Right: Protein condensates on different sides of the membrane become coupled. Representative images from lipid channels and cartoons showing fusion events of two uncoupled regions (b) and two coupled regions (c) of membrane-protein composites over time. d The aspect ratio changes over time during relaxation after the fusion of two regions. Red circles indicate aspect ratio change for uncoupled regions and blue circles for coupled regions. The dotted lines represent an exponential fit: y(t) = A + B*exp(-t/τ). e Images in the lipid channel showing fluorescence recovery for protein-depleted, uncoupled, and coupled regions. Yellow arrows indicate photobleached regions. f FRAP profile for the control (protein-free membrane, red circles, n = 5), Protein-depleted (blue triangles, n = 16), uncoupled (green diamonds, n = 17), and coupled (black squares, n = 6) regions. g Corresponding t_1/2, time required for 50% of fluorescence recovery, from FRAP profile in f. h Left: Lipid channel image showing both brighter and dimmer regions for calculating the partition coefficient of the lipid probe. Right: Partition coefficients (K_P) as a function of NaCl concentrations. (n = 50 from 3 independent experiments for each condition). Data are presented as mean values ± SD (f–h) i Schematic of our observation that protein condensates create lipid regions with reduced lipid mobility. Brackets in g and h show statistically significant comparisons using an unpaired, two-tailed Student’s t test. Above each bracket are p-values. Membrane composition: 85 mol% DOPC, 15 mol% DGS-Ni-NTA with 0.5 mol% Texas Red-DHPE (b, c, h) or NBD-PC (e). 1 µM of unlabeled his-RGG was used. Scale bars, 5 µm. Source data are provided as a Source Data file.