TGFβ receptors are single pass serine/threonine kinase receptors. They exist in several different isoforms that can be homo- or heterodimeric. The number of characterized ligands in the TGFβ superfamily far exceeds the number of known receptors, suggesting the promiscuity that exists between the ligand and receptor interactions.
Three TGF-β receptor types can be distinguished by their structural and functional properties. Receptor types I and II have similar ligand binding affinities and can only be distinguished from each other by peptide mapping, both receptor types I and II have a high affinity for TGF-β1 and low affinity for TGF-β2. TGF-β receptor type III has a high affinity for both TGF-β1 and -β2 and in addition TGF-β1.2.
↑Heteromeric and homomeric transforming growth factor-beta receptors show distinct signaling and endocytic responses in epithelial cells. J Biol Chem. 1998 Nov 27; 273(48): 31770-7; PMID9822641Free text
↑Cheifetz S, Andres JL and Massague J. (1988). "The transforming growth factor-beta receptor type III is a membrane proteoglycan". J. Biol. Chem. 263 (32): 16984–16991. PMID 2903157.