Bone morphogenetic protein (BMP) type I receptor that is involved in a wide variety of biological processes, including bone, heart, cartilage, nervous, and reproductive system development and regulation. As a type I receptor, forms heterotetrameric receptor complexes with the type II receptors AMHR2, ACVR2A ors ACVR2B. Upon binding of ligands such as BMP7 or BMP9 to the heteromeric complexes, type II receptors transphosphorylate ACVR1 intracellular domain. In turn, ACVR1 kinase domain is activated and subsequently phosphorylates SMAD1/5/8 proteins that transduce the signal. In addition to its role in mediating BMP pathway-specific signaling, suppresses TGFbeta/activin pathway signaling by interfering with the binding of activin to its type II receptor. Besides canonical SMAD signaling, can activate non-canonical signaling pathways. 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 FKBP1A. Interacts with FCHO1. Interacts with CLU. Interacts with type II receptors AMHR2 and ACVR2A. Interacts with BMP7. Interacts with BMP9. Interacts with BMP6. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. TGFB receptor subfamily.