Fig. 2.

Activation of latent myostatin activity by BMP-1/TLD proteinases. (A) Activation of pGL3-(CAGA)₁₂-luciferase reporter gene activity by purified myostatin C-terminal dimer. (B) Activation of the myostatin propeptide/C-terminal dimer latent complex by heat treatment. (C and D) Activation of the myostatin (MSTN) propeptide/C-terminal dimer latent complex by BMP-1/TLD proteinases. A standard curve using purified myostatin C-terminal dimer was generated for each set of assays to quantify myostatin activity. The samples used for the reporter assays in C and D are the same samples shown in Fig. 1 D and E, respectively. In B-D, black bars represent WT, and pink bars represent D76A mutant complexes. Note that, although heat treatment activated both the WT and mutant complexes, each proteinase was capable of activating only the WT complex. *, P < 0.05; **, P < 0.01. RLU, relative light units.