Figure 3.

From the C-terminal half of human P-gp only, the ECL4 is required for the binding of UIC2, MRK-16 and 4E3 antibodies. The 2-D topologies of the human-mouse P-gp chimeras are depicted (left). The N-terminal halves of the first four chimeras (A–D), which include the first three extracellular loops, are human (HH) and are shown in blue. The MMHH-ECL1-h5 chimera (E), contains in addition to five human amino acids in ECL1 in the first half (MM), the second half of the human P-gp (HH). The number of mutations and their locations are listed in Table 1. Representative histograms of flow cytometry analysis of antibody binding to different P-gp chimeras are shown. Other details are the same as given in the legend to Fig. 2.