Figure 12. Mutant S480C shows impeded ability to interact with TGF-β receptors in the membrane.

Interaction of mutant endoglin^S480C (FRET acceptor, false coloured in red) with the TGFB receptors (FRET donor, false coloured in green) is strongly reduced, although the relative trend is the same as seen before for endoglin^wt. The strongest interaction was measured between S480C and TβRII, followed by ALK5. FRET signals can be observed in vesicles (V) and for the cell membrane (M). Interaction of endoglin^S480C with ALK1 is lost, there is no positive FRET. Unspecific FRET occurrence is shown by the blue colour in the merged image. Co-expression of endoglin^S480C and endoglin^wt produces the highest FRET signals due to intra- and intermolecular FRET within heterodimers and between homodimers.