Fig. 3: Flotillin complex mediated membrane compartmentalization.

a–d SPFH1 domains of flotillin-1 and flotillin-2 are inserted in the cytoplasmic leaflet of the membrane. Flotillin-1 and flotillin-2 are colored cyan and yellow, respectively. Detergent density is colored gray. a Vertical cross-section view of the atomic model of the flotillin complex with the low-pass filtered cryo-EM density map of detergent micelle superimposed, in the position of the axis of symmetry. b Horizontal cross-section view of the low-pass filtered cryo-EM density map of the flotillin complex with detergent micelle, in the position of the SPFH1 region. Protomers of flotillin-1 and flotillin-2 are numbered anti-clockwisely. c Zoomed-in view of the SPFH regions of the flotillin complex. d Zoomed-in view of the SPFH1 regions of the flotillin complex with ninety-degree rotation, with the removal of detergent density in the foreground. Aromatic residues (F2, F3, F16 and F30 of flotillin-1; W32, W34, W36 and W37 of flotillin-2) are inserted in the membrane. Cystine residues (C34 of flotillin-1; C4, C19 and C20 of flotillin-2), which are reported to be palmitoylated, and glycine residue (G2 of flotillin-2), which is reported to be myristoylated, are all buried in membrane. e Hydrophobic surface model of the SPFH regions from a flotillin-1/2 dimer within the complex. The PTMs in this region are not considered here. Cyan, hydrophilic; white, neutral; gold, hydrophobic. f Side views and top views of deformed maps during cryo-EM single-particle analysis (SPA) 3D classification. The slabs of these maps are shown aside, as illustrated in Supplementary Fig. 2d, e.