In order to be functional, BCRP must exist in a multimer (usually a homodimer). The purple and pink structures are the dimers, while the off-white is 5D3-Fab (included to depict orientation). The extracellular region is at the top while the bottom in the intracellular region. Domains
Let's look at the three domains of BCRP. The region with dense and vertical alpha helices spans the membrane, as one would expect.
Polarity and Charge
Here, BCRP is shown with the positively charged residues pink, the negatively charged residues blue, the polar residues purple, and the nonpolar residues white.
Taylor, Nicholas M.I., et al.
Structure of the human multidrug transporter ABCG2.
Nature. 2017 Jun 22;546(7659):504-509 (PubMed)
1xme (PDB)