On ligand binding, forms a receptor complex consisting of two type II and two type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate, then bind and activate SMAD transcriptional regulators. Receptor for BMP7/OP-1. Receptor for GDF5 (PubMed:26105076, PubMed:19229295). Positively regulates chondrocyte differentiation through GDF5 interaction (PubMed:24098149). ATP + L-threonyl-[receptor-protein] = ADP + H(+) + O-phospho-L-threonyl-[receptor-protein] ATP + L-seryl-[receptor-protein] = ADP + H(+) + O-phospho-L-seryl-[receptor-protein] Interacts with high affinity with GDF5; positively regulates chondrocyte differentiation. Interacts with SCUBE3. Autophosphorylated. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. TGFB receptor subfamily.