Figure 7. Structure of afTMEM16 in the presence of C24:0 ceramide.

(A) Structural alignment of Ca²⁺-bound afTMEM16 with (light blue) and without C24:0 ceramide (maroon) with a Cα r.m.s.d. <1 Å. (B) The unmasked maps (gray) of the afTMEM16/nanodisc complex in the presence of 0.5 mM Ca²⁺ and 5 mol% C24:0 ceramide is shown low pass filtered to 10 Å at σ = 0.4 with front (left panel) and back (right panel) views. The masked map of the afTMEM16 scramblase in 0.5 mM Ca²⁺ and 5 mol% C24:0 ceramide is shown inside the respective unmasked maps. Red dashed lines highlight the membrane bending. (C) Top view of unmasked map (grey) low pass filtered to 10 Å at σ = 0.1 with the atomic models inside. Insets show the density at the permeation pathway. Note that the insets are displayed at a tilted angle compared to the top views to visualize the changes in density at the lipid pathway.

Figure 7—figure supplement 1. Lipid-like density in the dimer cavity.

Atomic model of afTMEM16 in in the presence of 0.5 mM Ca²⁺ and 5 mole% C24:0 Ceramide with location of lipid acyl chains within the side dimer cavity. Insets show acyl chains colored by ligand ID (D12-green, D10-blue, 8K6-cyan, OCT-teal) into the difference map density (in red) between the experimental density map and the theoretical map calculated from the model with lipids omitted. Only the lipids in one dimer cavity are shown for clarity.