Nature may use charge burial to reduce protein stability; not all buried charges are fully stabilized by a prearranged protein environment. Consistent with this view, thermophilic proteins often have less buried charge. Modifying the amount of buried charge at carefully chosen sites may thus provide a general route for changing the thermophilicity or psychrophilicity of proteins.

The results of investigations in these laboratories of 2-aryl-4-(piperidin-1-yl)butanamines and 1,3,4-trisubstituted pyrrolidines as human CCR5 antagonists have recently been disclosed. To facilitate further development of these antagonists, we have developed a pharmacophore model based on the structure-activity relationships (SAR) and a human CCR5 receptor docking model using the crystal structure of rhodopsin as a template [Palczewski, K., et al. (2000) Science 289, 739-745]. Guided by the receptor docking model, we have mapped the compounds' site of interaction with CCR5 using site-directed mutagenesis experiments. Our results are consistent with a binding site for the two series that is located within a cavity near the extracellular surface formed by transmembrane helices 2, 3, 6, and 7. This site is overlapping yet distinct from that reported for another antiviral agent which binds to CCR5 [Dragic, T., et al. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 5639-5644].