FIGURE 2.

Point mutations to IH1 do not inhibit P-gp maturation. A, the location of coupling helix IH1 between TMD1 and NBD1 is shown in the model. B, whole cell SDS extracts of HEK 293 cells expressing wild-type P-gp and P-gp mutants (mutations to IH1 and flanking regions) were subjected to immunoblot analysis. The positions of mature (170 kDa) and immature (150 kDa) forms of P-gp are shown. C, verapamil-stimulated ATPase activities of wild-type P-gp and mutants predicted to form contacts between IH1 and NBD1 in the C. elegans P-gp crystal structure (17). The results are the mean of three different transfections + S.D.