The structure of the follistatin:activin complex reveals antagonism of both type I and type II receptor binding.

TGF-beta ligands stimulate diverse cellular differentiation and growth responses by signaling through type I and II receptors. Ligand antagonists, such as follistatin, block signaling and are essential regulators of physiological responses. Here we report the structure of activin A, a TGF-beta ligand, bound to the high-affinity antagonist follistatin. Two follistatin ...
molecules encircle activin, neutralizing the ligand by burying one-third of its residues and its receptor binding sites. Previous studies have suggested that type I receptor binding would not be blocked by follistatin, but the crystal structure reveals that the follistatin N-terminal domain has an unexpected fold that mimics a universal type I receptor motif and occupies this receptor binding site. The formation of follistatin:BMP:type I receptor complexes can be explained by the stoichiometric and geometric arrangement of the activin:follistatin complex. The mode of ligand binding by follistatin has important implications for its ability to neutralize homo- and heterodimeric ligands of this growth factor family.
Mesh Terms:
Activin Receptors, Type I, Activins, Amino Acid Sequence, Animals, Binding Sites, Cricetinae, Crystallography, X-Ray, Follistatin, Inhibin-beta Subunits, Ligands, Models, Molecular, Molecular Sequence Data, Multiprotein Complexes, Protein Binding, Protein Isoforms, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Receptors, Transforming Growth Factor beta, Sequence Alignment, Transforming Growth Factor beta
Dev. Cell
Date: Oct. 01, 2005
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