The Transforming Growth Factor-β Receptor (TGF-βR) family are transmembrane serine/threonine kinases. They form heterodimeric receptor complexes composed of type I and type II subunits. Upon ligand binding, the type I receptor is phosphorylated by the constitutively active type II receptor, activating the type I receptor which, in turn, phosphorylates a member of the Smad family. In Drosophila, TGF-β receptor ligands belong to the bone morphogenetic protein (BMP) or activin families. (Adapted from
FBrf0236482.)
