. "The transforming growth factor beta (TGF-beta) family of cytokines regulates cell proliferation, differentiation, recognition and death." . "Signaling occurs by the binding of ligand to the type II receptor, which is the constitutively active kinase." . "Bound TGF-beta is then recognized by receptor I, which is phosphorylated and can propagate the signal to downstream substrates." . . . "Receptor protein serine/threonine kinase" . "Activin receptor kinase" . "Receptor serine/threonine protein kinase" . "Receptor type I serine/threonine protein kinase" . "Receptor type II serine/threonine protein kinase" . "TGF-beta kinase" . . "ATP + [receptor-protein] = ADP + [receptor-protein] phosphate." .