Figure 1.

(A) Schematic presentation of ABCG2 topology. (B) Schematic presentation of HA-tagged full-length and Myc-tagged ABCG2 constructs. The solid circle and ovals represent HA and Myc tags, respectively. The numbered boxes and lines represent transmembrane (TM) segments and loops (L), respectively. Abbreviations: ECL, extracellular loop; NBD, nucleotide-binding domain; MSD, membrane-spanning domain. (C) Co-IP. HEK293 cells with stable expression of ABCG2^HA-WT were transiently transfected with ABCG2^Myc-TM5–6, ABCG2^Myc-TM1–2, or ABCG2^{Myc-TM1–2/L1*} followed by immunoprecipitation with the Myc antibody and Western blot analysis of the precipitates with HA and Myc antibodies. (D) Quantitative analysis of Co-IP. The expression and Co-IP level of constructs from three independent experiments as shown in panel C were quantified using ScnImage and calculation of the relative ratio of Co-IP to the expression level followed by normalization to that of the positive control construct ABCG2^Myc-TM5–6.