Model for BCD effects on CCR5 conformation.

The diagrams show CCR5 from a top view, as if looking down onto a cell membrane. Cholesterol normally interacts with transmembrane domains of CCR5, providing a relatively rigid structure capable of binding MIP-1β. Cholesterol extraction by BCD alters the overall conformation of the receptor, changing the MIP-1β binding site and epitopes required for mAb recognition. The increase in membrane fluidity is also likely to increase protein fluidity, resulting in poor mAb binding. Individual loops may also have altered conformations as a result of cholesterol extraction. With fixation, protein rigidity is restored, which in turn restores mAb binding.