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Updated: Aug 24, 2025
X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
Helical ultrastructure of the metalloprotease meprin α in complex with a small molecule inhibitor
Charles Bayly-Jones1,2, Christopher J Lupton1,2, Claudia Fritz3
1Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, Australia.
Abstract:
The zinc-dependent metalloprotease meprin α is predominantly expressed in the brush border membrane of proximal tubules in the kidney and enterocytes in the small intestine and colon. In normal tissue homeostasis meprin α performs key roles in inflammation, immunity, and extracellular matrix remodelling. Dysregulated meprin α is associated with acute kidney injury, sepsis, urinary tract infection, metastatic colorectal carcinoma, and inflammatory bowel disease. Accordingly, meprin α is the target of drug discovery programs. In contrast to meprin β, meprin α is secreted into the extracellular space, whereupon it oligomerises to form giant assemblies and is the largest extracellular protease identified to date (~6 MDa). Here, using cryo-electron microscopy, we determine the high-resolution structure of the zymogen and mature form of meprin α, as well as the structure of the active form in complex with a prototype small molecule inhibitor and human fetuin-B. Our data reveal that meprin α forms a giant, flexible, left-handed helical assembly of roughly 22 nm in diameter. We find that oligomerisation improves proteolytic and thermal stability but does not impact substrate specificity or enzymatic activity. Furthermore, structural comparison with meprin β reveal unique features of the active site of meprin α, and helical assembly more broadly.
Insights
Meprin α, a large extracellular protease, forms giant helical assemblies. These structures enhance stability without altering enzymatic activity, offering insights for drug discovery targeting diseases like kidney injury and cancer.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Medicine
Background:
- Meprin α is a zinc-dependent metalloprotease crucial for tissue homeostasis.
- Its dysregulation is linked to kidney injury, sepsis, and colorectal carcinoma, making it a drug discovery target.
- Unlike meprin β, meprin α is secreted and forms large extracellular assemblies.
Purpose of the Study:
- To determine the high-resolution structure of meprin α in its zymogen, mature, and active forms.
- To investigate the structural basis of meprin α's giant helical assembly.
- To analyze the complex of active meprin α with an inhibitor and fetuin-B.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was used to determine the structures.
- Structural comparisons were made between meprin α and meprin β.
- Inhibitor and substrate interactions were analyzed structurally.
Main Results:
- Meprin α forms a giant, flexible, left-handed helical assembly (~22 nm diameter).
- Oligomerization enhances proteolytic and thermal stability but not substrate specificity or activity.
- Unique active site features and helical assembly mechanisms were revealed compared to meprin β.
Conclusions:
- The study provides the first high-resolution structures of meprin α assemblies.
- Understanding meprin α's structure-function relationship is vital for developing targeted therapeutics.
- The findings offer insights into the unique assembly and stability of this large extracellular protease.
