6UMX

Structural basis for specific inhibition of extracellular activation of pro/latent myostatin by SRK-015

Summary for 6UMX

• Entry DOI: 10.2210/pdb6umx/pdb
• Descriptor: Growth/differentiation factor 8, GL29H4-16 Fab Light Chain,GL29H4-16 Fab Light Chain, GL29H4-16 Fab Heavy Chain,GL29H4-16 Fab Heavy Chain, ... (5 entities in total)
• Functional Keywords: myostatin, gdf8, transforming growth factor beta, muscle wasting disease, antibody, fab, signaling protein-immune system complex, signaling protein/immune system
• Biological source: Homo sapiens (Human); More
• Total number of polymer chains: 6
• Total formula weight: 178140.31

Authors

Dagbay, K.B.,Treece, E.,Streich Jr., F.C.,Jackson, J.W.,Faucette, R.R.,Nikiforov, A.,Lin, S.C.,Bostion, C.J.,Nicholls, S.B.,Capili, A.D.,Carven, G.J. (deposition date: 2019-10-10, release date: 2020-02-26, Last modification date: 2024-11-20)

Primary citation

Dagbay, K.B.,Treece, E.,Streich Jr., F.C.,Jackson, J.W.,Faucette, R.R.,Nikiforov, A.,Lin, S.C.,Boston, C.J.,Nicholls, S.B.,Capili, A.D.,Carven, G.J.
Structural basis of specific inhibition of extracellular activation of pro- or latent myostatin by the monoclonal antibody SRK-015.
J.Biol.Chem., 295:5404-5418, 2020

PubMed Abstract: Myostatin (or growth/differentiation factor 8 (GDF8)) is a member of the transforming growth factor β superfamily of growth factors and negatively regulates skeletal muscle growth. Its dysregulation is implicated in muscle wasting diseases. SRK-015 is a clinical-stage mAb that prevents extracellular proteolytic activation of pro- and latent myostatin. Here we used integrated structural and biochemical approaches to elucidate the molecular mechanism of antibody-mediated neutralization of pro-myostatin activation. The crystal structure of pro-myostatin in complex with 29H4-16 Fab, a high-affinity variant of SRK-015, at 2.79 Å resolution revealed that the antibody binds to a conformational epitope in the arm region of the prodomain distant from the proteolytic cleavage sites. This epitope is highly sequence-divergent, having only limited similarity to other closely related members of the transforming growth factor β superfamily. Hydrogen/deuterium exchange MS experiments indicated that antibody binding induces conformational changes in pro- and latent myostatin that span the arm region, the loops contiguous to the protease cleavage sites, and the latency-associated structural elements. Moreover, negative-stain EM with full-length antibodies disclosed a stable, ring-like antigen-antibody structure in which the two Fab arms of a single antibody occupy the two arm regions of the prodomain in the pro- and latent myostatin homodimers, suggesting a 1:1 (antibody:myostatin homodimer) binding stoichiometry. These results suggest that SRK-015 binding stabilizes the latent conformation and limits the accessibility of protease cleavage sites within the prodomain. These findings shed light on approaches that specifically block the extracellular activation of growth factors by targeting their precursor forms.

PubMed: 32075906
DOI: 10.1074/jbc.RA119.012293

Experimental method

X-RAY DIFFRACTION (2.79 Å)