Twisted Gastrulation Protein (TSG) is a secreted BMP-binding protein that is structurally related to the BMP antagonists Chordin and Noggin. TSG can inhibit BMP activity by binding directly to BMP proteins, and can act either as a BMP-4 agonist or antagonist (depending on the specific biochemical environment) by binding to the BMP-4/Chordin complex. Recombinant Human TSG is a 198 amino acid, 22.2 kDa protein containing the BMP/TGF-beta binding portion of the full length TSG protein.