Fig. 1: Overall structures of BMP10:BMPRII and ALK1:BMP10:BMPRII complexes.

a One asymmetric unit of the BMP10:BMPRII 1.48 Å crystal structure. Chain identities (IDs) A to D are labelled. BMP10 is coloured in coral and light purple, BMPRII coloured in green. b 2.4 Å structure of BMP10:BMPRII with chain IDs labelled. Only one monomer of BMP10 (in coral) and BMPRII (in green) in an asymmetric unit. One symmetry-related molecule is shown in grey to illustrate the BMP10 dimer bound to two copies of BMPRII. c–e Overall structure of the ALK1:BMP10:BMPRII complex. Four copies of each BMP10, ALK1 and BMPRII monomers are found in one asymmetric unit, forming two copies of ternary signalling complexes shown in semi-transparent yellow and grey surface. Chain IDs in complex 1 (cpx1) (d) and cpx2 (e) are shown. In cpx1, BMP10 monomers are coloured in coral and light purple, ALK1 in yellow and BMPRII coloured in green. In cpx2, BMP10 monomers are coloured in coral and cyan, ALK1 in dark yellow, BMPRII in green. f An illustration of BMPRII-signalling complex in relation to cell surface. The last residues in ALK1 and BMPRII ECD cDNA-encoded sequences are 118 and 150, respectively. The last residues that can be seen in the crystal structures are shown in spheres and labelled. The 1.48 Å BMP10:BMPRII structure (in grey and semi-transparent) is superimposed on the ternary signalling complex (coloured as in Fig. 1d, cpx1) to show positions of further modelled sequence in BMPRII C-termini. The C-terminal 10–13 residues in both ALK1 and BMPRII that are not visible in the structure are represented by thick dashed lines.