Figure 2. Cholesterol-binding domains of StAR and TSPO.
A) Human StAR protein modeled with cholesterol (brown) present in the sterol-binding domain (PDB ID code: 2I93). Homology models are deduced via the Swiss-model services under project (optimize) mode using the crystal structures of human MLN64 (PDB ID code: 1EM2) as template (http://swissmodel.expasv.org/SWISS-MODEL.html. B) Molecular model of TSPO’s five alpha helices in the presence of cholesterol, demonstrating a pore accommodating a cholesterol molecule. Homology modeling of mouse TSPO was performed using apolipophorin-III from Manduca sexta as template (PDB ID code: 1EQ1) [158]. C) Ribbon diagram of mTSPO, showing the five helices as well as the CRAC domain, consisting of Leu/Tyr/Arg residues, and cholesterol (top view). D) Docking model of cholesterol to the TSPO CRAC domain. The accessible surface of the peptide and cholesterol molecules are represented in red and blue, respectively (Reprinted with permission from [159]).