CC chemokine receptor 4（CCR4） is a G-protein-coupled receptor which plays a pivotal role in allergic inflammation. In the present study, three extracellular loops（EL1-3） of CCR4 were synthesized, and the interactions between the extracellular loops and compound S009 were investigated using capillary zone electrophoresis（CZE）. Both qualitative and quantitative characterizations of the compound-peptide binding were carried out. The experimental data indicated that compound S009 exhibited interactions with EL3, and a binding constant of（12.5±0.19）×10^4 M^-1 was determined using the Scatchard plot. Our study identified the specific domains of CCR4 that could be targeted by small molecules and provided insights for the discovery of novel CCR4 antagonists.
