Description
Cellular responses to bone morphogenetic proteins (BMPs) have been shown to be mediated by the formation of hetero-oligomeric complexes of the type I and type II serine/threonine kinase receptors. BMPR1A is one of seven known type I serine/threonine kinases that are required for the signal transduction of the TGF-b family cytokines. In contrast to the TGF-b receptor system in which the type I receptor does not bind TGF-b in the absence of the type II receptor, type I receptors involved in BMP signaling (including BMPR1A, BMPR1B/ALK6, and ActR-I/ALK2) can independently bind the various BMP family proteins in the absence of type II receptors. Recombinant soluble BMPR1A binds BMP2 and -4 with high-affinity in solution and is a potent BMP2/4 antagonist in vitro. BMPR1A is ubiquitously expressed during embryogenesis. In adult tissues, BMPR1A mRNA is also widely distributed, with the highest expression levels found in skeletal muscle. The extracellular domain of BMPR1A shares little amino acid sequence identity with the other mammalian ALK type I receptor kinases, but the cysteine residues are conserved. Human and mouse BMPR1A are highly conserved and share 98% sequence identity