Growth/differentiation factor 8 (GDF8), or myostatin, negatively regulates muscle mass. GDF8 is held in a latent state through interactions with its N-terminal prodomain. GDF8, like numerous TGF-β family members, is a disulfidelinked dimer that is synthesized as a precursor protein which requires cleavage by a furin-like protease to yield an N-terminal prodomain and a C-terminal mature, signaling domain.

> 95% as determined by Bis-Tris PAGE; > 90% as determined by HPLC