CETP (Cholesteryl Ester Binding Protein) was resolved by the group at 2.2 A. It contains a long hydrphobic tunnel (~60 A) which sequesters its hydrophobic cargo and shields it from the aqueous environment of the blood. The entrances of the tunnel are blocked by the polar head group of a lipid- oleaylphosphatidyl choline. Remarkably, the group managed to crystallize the protein with four different molecules, all of which are important in lipid metabolism- cholesteryl oleate, triglycerides, and phoshatidyl choline. The overall shape of the protein is like a boomerang, and the authors surmise that the shape could help to latch on to an HDL particle.
It is sad that Torcetrapid failed. The binding of the drug had been intensively studied, and its potency had been evaluated with a high degree of confidence. In the end, the drug sank in the one foggy area where human prediction still fails- toxicity and side effects. The company has redeemed itself to some extent with this structure and hopefully, the structure will lead them to a safer version or analog of torcetrapib. Till then, it does no harm to study the structure for the sake of beauty alone.