Type III serine/threonine kinase is often referred to as an accessory protein. While it has no known enzymatic activity, it can regulate the signalling of RSTKs [1-2].

1. Hill CR, Jacobs BH, Brown CB, Barnett JV, Goudy SL. (2015) Type III transforming growth factor beta receptor regulates vascular and osteoblast development during palatogenesis. Dev Dyn, 244 (2): 122-33. [PMID:25382630]

2. López-Casillas F, Cheifetz S, Doody J, Andres JL, Lane WS, Massagué J. (1991) Structure and expression of the membrane proteoglycan betaglycan, a component of the TGF-beta receptor system. Cell, 67 (4): 785-95. [PMID:1657406]