FIG. 3.

Affinity of RANTES variants for CCR5 measured by competition binding assay on CHO-CCR5 cells. The selected mutants P1 and P2 have significantly higher affinity for CCR5 than either RANTES or AOP-RANTES. With [¹²⁵I]MIP-1β used as a tracer (top panel), IC₅₀ of 9.0, 9.5, 0.56, and 0.18 nM were observed for RANTES, AOP-RANTES, P1, and P2, respectively. With [¹²⁵I]RANTES used as a tracer (bottom panel), the respective IC₅₀ were 4.1, 3.9, 2.0, and 0.18 nM.