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 (PubMed:20628059, PubMed:22977237). As a type I receptor, forms heterotetrameric receptor complexes with the type II receptors AMHR2, ACVR2A or ACVR2B (PubMed:17911401). Upon binding of ligands such as BMP7 or GDF2/BMP9 to the heteromeric complexes, type II receptors transphosphorylate ACVR1 intracellular domain (PubMed:25354296). In turn, ACVR1 kinase domain is activated and subsequently phosphorylates SMAD1/5/8 proteins that transduce the signal (PubMed:9748228). 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 (PubMed:17911401). Besides canonical SMAD signaling, can activate non-canonical pathways such as p38 mitogen-activated protein kinases/MAPKs (By similarity). 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 (PubMed:22484487, Ref.12). Interacts with FCHO1 (PubMed:22484487). Interacts with CLU (PubMed:8555189). Interacts with type II receptors AMHR2 and ACVR2A (PubMed:17911401). Interacts with BMP7 (PubMed:9748228). Interacts with GDF2/BMP9 (PubMed:20628059). Interacts with BMP6 (PubMed:18070108). Expressed in normal parenchymal cells, endothelial cells, fibroblasts and tumor-derived epithelial cells. The disease is caused by variants affecting the gene represented in this entry. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. TGFB receptor subfamily.