Methyl-Labeling Assisted NMR Structure Determination of a 66 KDA Growth Factor-Receptor Complex

TGF-β1, TGF- β2, and TGF-β3 are 26 kDa disulfide-linked homodimeric signaling proteins. They all signal through the TGF-β type I and type II receptors, yet TGF-β2, which is well known to bind TβRII several-hundred fold more weakly than TGF-β1 and TGF-β3, has an additional requirement for the TGF-β type III receptor (TβRIII), a membrane-anchored non-signaling receptor that potentiates the binding of TβRII. Though it is known that TβRIII has two component domains that bind TGF-β2 non-cooperatively at independent sites, the structure of these domains bound to TGF-β2 and residues responsible for specific binding are not yet known.