BiFC principle and ABCG2 BiFC constructs employed.

A The underlying principle of BiFC is the refolding and maturation of a chromophore (here vYFP) that occurs upon the interaction of two proteins (here shown as cylinders) bearing complementary fragments of the YFP protein (red and blue interlocking shapes). B In the current manuscript, ABCG2 comprised of a N-terminal nucleotide binding domain (orange) and a C-terminal TMD (olive green) is tagged with either full length YFP variants (yellow circles), or with complementing fragments of YFP variants, shown as red and blue hemispheres. The tagging of YFP and fragments was at either the 5′ (N-terminus) or the 3′ (C-terminus) of the ABCG2 cDNA.