NTRK1 and breast cancer: It turned out that the insertion of the C-terminal part of the fluorescent protein (GC, the C-terminal fragment of GFP was used in this case, because BiFC was more easily detected by fluorescence microscopy visualisation with the setup used) into the intracellular loop three between MPM motifs C and D (Trk1[ΔLHL][G1010/GC/E1011]) in combination with Trk1[ΔLHL]/VN (Figure 5A) would allow BiFC only for BC/CB and CD/DC dimers and tetramers with A or B in the centre but not with dimers AB/BA and DA/AD and with tetramers C and D (Figure 5B).