 In addition to rationalizing a large number of HHT1 mutations, the crystal structure of endoglin shows that the epitope of anti-ENG monoclonal antibody TRC105 overlaps with the binding site for BMP-9.Endoglin has been shown to interact with high affinity to TGF beta receptor 3 and TGF beta receptor 1, and with lower affinity to TGF beta receptor 2.It has high sequence similarity to another TGF beta binding protein, beta-glycan, which was one of the first cues that indicated that endoglin is a TGF beta binding proteins.