Fig. 3: Higher-order TRIM72 assembly on the lipid bilayer.
From: Structure and activation of the RING E3 ubiquitin ligase TRIM72 on the membrane
a, Cryo-ET maps of the reconstituted TRIM72 proteoliposome. Top view (left) and front view (right) are shown with subtomogram averaging reconstruction density contoured at 1 σ. b, Higher-order TRIM72-assembly model on the lipid bilayer. Top left, front view (perpendicular to the lipid surface) of the TRIM72-assembly model with a subtomogram averaging map contoured at 1 σ. Top right, the black box in the front view is enlarged to a close-up view. The top view (parallel to the lipid surface, bottom left) and a sliced view (bottom right) of the TRIM72 assembly. The black boxes in the top view are represented as ribbon diagrams in d,e. The highlighted TRIM72 protomers in the dimer are colored red and blue, respectively. The lipid bilayer models are shown in stick representation in green (top right). Subtomogram averaging reconstruction maps of the TRIM72 assembly and lipid bilayer are colored in white and pink, respectively. c, Assembly pattern of TRIM72 as observed in subtomogram averaging reconstruction. Averages of z slices correspond to the middle and front view in b. The relative intensities according to the y axis (right; red) and the x axis (bottom; blue) were calculated from the averaged z slices of the front view. Numbers in italics (1–5) indicate each column-like density corresponding to the PRYSPRY ___domain. Note that the regular intervals between the PRYSPRY densities are 6 nm (bottom). Black scale bars, 5 nm in a–c. d, Interface between B-boxes. Interacting residues and zinc ions are shown in stick and sphere models, respectively. e, Interface between H1 helices in the CCDs. f, Circle plots of cross-linked cysteine residues of TRIM72 with or without PS liposomes. Frequently identified cross-linked pairs are shown as thick lines. Homotypic cysteine-bridged pairs are shown in red and were identified in the presence of PS liposomes. g, Liposome co-sedimentation assay of TRIM72 WT and mutants. The experimental scheme is shown at the top; the image was created with BioRender.com. PC liposomes, phosphatidylcholine-containing liposomes; pel, pellet; sup, supernatant.
