Figure 3
BMP-2 type I receptor interface. (a) The tilt angle of BMPR-IA bound to BMP-2 changes upon binding of the type II receptor ActR-IIB. A superposition of the structures of BMP-2:(BMPR-IAECD)2 (blue, PDB entry 1REW), the ternary complex (1:1:1) of wildtype BMP-2:BMPR-IAECD:ActR-IIBECD (green) and the ternary complex (1:2:2) of BMP-2L100K/N102D:(BMPR-IAECD)2:(ActR-IIBECD)2 (red) is shown. The comparison of both assemblies reveals that the rearrangement is not due to the mutations introduced in BMP-2L100K/N102D. (b) A change in the backbone conformation of residues 86 to 88, and 100 to 105 located in the finger 2 of BMP-2 is the possible cause for the tilt angle change. The type I ligand-receptor interfaces of the ternary (1:1:1) (c) and (1:2:2) (d) BMP-2/receptor complexes are structurally almost identical differing only in very few H-bonds that are located at the solvent accessible surface.