Growth differentiation factor 2 (GDF2) also known as bone morphogenetic protein (BMP)-9 is a protein that in humans is encoded by the GDF2 gene. GDF2 belongs to the transforming growth factor beta superfamily.
GDF2 contains an N-terminal TGF-beta-like pro-peptide (prodomain) (residues 56–257) and a C-terminal transforming growth factor beta superfamily domain (325–428). GDF2 (BMP9) is secreted as a pro-complex consisting of the BMP9 growth factor dimer non-covalently bound to two BMP9 prodomain molecules in an open-armed conformation.