Fig. 1

Schematic of native BMP production and heterodimer fabrication. A Schematic of the production and function of a BMP growth factor. (i) BMPs are produced as a single polypeptide chain consisting of a larger prodomain (30–40 kDa, dark blue) and a smaller (12–14 kDA, light blue) mature domain. (ii) Prodomain interactions bring the mature domains together and induce dimerization, which is stabilized by an inter-chain disulfide bond. (iii) representation of the mature ligand and shown in iv) bound to two high-affinity type 1 receptors (yellow) and two low-affinity type 2 receptors (orange). B Schematic of differences in type 1 interfaces of homo- and hetero-dimers. The heterodimer (BMP chain in blue and GDF5 chain in green) consists of two unique binding sites, one formed by the fingers of BMP and the wrist of GDF5 and one formed by the fingers of GDF5 and wrist of BMP, as annotated. C Heparin affinity chromatography is used to separate refolded homodimeric GDF5 (green) and homodimeric BMP2 (blue) from BMP2/GDF5 heterodimer (purple) based on differential heparin binding affinity. Presence of pure homodimeric and heterodimeric proteins confirmed by SDS-PAGE and western blot analysis, under both reducing and non-reducing conditions. D Heparin affinity chromatography is used to separate refolded homodimeric GDF5 (green) and homodimeric BMP4 (blue) from BMP4/GDF5 heterodimer (purple) based on differential heparin binding affinity. Presence of pure homodimeric and heterodimeric proteins confirmed by SDS-PAGE and western blot analysis, under both reducing and non-reducing conditions. Protein ladder shown at 10 kDa, 17 kDa, 26 kDa, and 34 kDa