Fig. 7. Model of the stable SCD1-cyt b5-b5R complex.

SCD1 (cyan), cyt b₅ (red), and b₅R (orange) are shown as translucent surfaces highlighting the diiron center (orange sphere) and acyl-CoA (cyan stick) in SCD1, heme (deep red stick) in cyt b₅, and FAD (brown stick) in b₅R. SCD1 forms a complex with the TM helix of cyt b₅ and b₅R in lipid bilayer (yellow). The relative positions of two residues on the TM helix of cyt b₅ are marked. A flexible linker connecting the soluble domain of cyt b₅ and b₅R to their TM helix allows the transition of two states: a cyt b₅ receiving an electron from b₅R; and b cyt b₅ delivering an electron to SCD1.