Published Online September 12 2013 Science Express Science DOI: 10.1126/science.1241475 Report Structure of the CCR5 Chemokine Receptor–HIV Entry Inhibitor Maraviroc Complex full text Abstract The CCR5 chemokine receptor acts as a co-receptor for HIV-1 viral entry. Here, we report the 2.7 Å resolution crystal structure of human CCR5 bound to the marketed HIV drug Maraviroc. The structure reveals a ligand binding site that is distinct from the proposed major recognition sites for chemokines and the viral glycoprotein gp120, providing insights into the mechanism of allosteric inhibition of chemokine signaling and viral entry. A comparison between CCR5 and CXCR4 crystal structures, along with models of co-receptor/gp120-V3 complexes, suggests that different charge distributions and steric hindrances caused by residue substitutions may be major determinants of HIV-1 co-receptor selectivity. These high-resolution insights into CCR5 can enable structure-based drug discovery for the treatment of HIV-1 infection.