Fig. 1: Cryo-EM structure of human MBOAT7.

a Diagram depicting the Lands cycle and MBOAT7-mediated PI remodeling in the membrane. Newly synthesized PI contains mainly monounsaturated sn-2 acyl chains. Phospholipase A2 (PLA₂) hydrolyzes the sn-2 ester bond and produces lyso-PI. MBOAT7 specifically re-acylates lyso-PI with arachidonyl-CoA as the acyl donor to produce the remodeled PI molecules. The sn-2 hydroxyl group is highlighted in red. b Size-exclusion profile of purified MBOAT7 reconstituted in PMAL-C8. Inset left, SDS-PAGE analysis of the MBOAT7 peak. The arrowhead denotes the MBOAT7 band, which migrates faster than its 53-kDa mass. Inset right, activity analysis of the purified MBOAT7 protein with the fluorescence monitoring of the production of the byproduct CoA-SH (mean ± standard deviation [SD], n = 3 independent experiments). Analysis was performed using one-way ANOVA with Dunnett’s post hoc test. c Cryo-EM map of human MBOAT7. The amphipol micelle is shown as a transparent gray outline. Map is contoured at 6 σ. The map is rainbow-colored, corresponding the colors of secondary elements in the models in d. d Cylinder representation of the human MBOAT7 model. The red star indicates the catalytic residue His356. Dashed lines indicate the disordered C-terminal region. TM, transmembrane; IH, intervening helix. e Representation of MBOAT7 with an electrostatic surface. The inserts indicate the entries to the two tunnels from two sides of the membrane. Arrows indicate the specific features. f The topology of MBOAT7 in membranes. Top, Schematic depiction of the fluorescence protease protection (FPP) assay. Plasma membrane is permeabilized by low concentrations of digitonin without disrupting the ER membrane. Subsequent addition of proteinase K selectively cleaves the fluorescent proteins on the cytoplasmic side of the exposed ER membrane, leaving the fluorescent proteins exposed in the lumen intact. Bottom, the quantification of the fluorescence intensities of the whole time series of the FFP assay. The time points when digitonin or proteinase K were added were indicated (Mean ± standard error of the mean [SEM], n = 3 independent experiments). Source data are provided as a Source Data file.