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Updated: Mar 12, 2026
Author Spotlight: A Computational Approach to Decipher Amino Acid Preferences in Multispecific Protein-Protein Interactions
Published on: January 26, 2024
Downsizing the BAD BH3 peptide to small constrained α-helices with improved ligand efficiency
Nicholas E Shepherd1, Rosemary S Harrison1, Gloria Ruiz-Gomez2
1Centre of Excellence in Advanced Imaging, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld 4072, Australia. d.fairlie@imb.uq.edu.au n.shepherd@imb.uq.edu.au.
Abstract:
Bcl2 Homology (BH) proteins can either trigger or prevent programmed cell death or apoptosis. Deregulation of the BH protein family network leads to evasion of apoptosis, uncontrolled proliferation and is a hallmark of cancer. Inhibition of pro-survival BH proteins is a promising chemotherapeutic strategy for certain cancers. We have examined whether helix-constrained peptides based on the BAD BH3 domain (residues 103-127) can be downsized to much smaller more drug-like peptides. We report the preparation, structural characterisation, in vitro Bcl-xL inhibition and leukemic T-cell killing ability of 45 linear, mono-, bi- and tricyclic helical peptidomimetics between 8- and 19-residues in length. We show that the BAD BH3 can be downsized to 8-14 residues and still maintain appreciable affinity for Bcl-xL. In addition, the binding efficiency indices (BEI) of the downsized mimetics are significantly higher than the BAD BH3 and similar stapled BH3 mimetics, approaching drug-like molecules. This suggests that bicyclic and monocyclic mimetics based on BH3 domains are much more efficient binding ligands than the longer peptides which they mimic.
Insights
Researchers developed smaller, drug-like peptides that inhibit pro-survival Bcl2 Homology (BH) proteins, a key target in cancer therapy. These novel BH3 mimetics effectively kill leukemic T-cells by binding strongly to Bcl-xL.
Area of Science:
- Biochemistry
- Molecular Biology
- Medicinal Chemistry
Background:
- Bcl2 Homology (BH) proteins regulate apoptosis, and their dysregulation is a hallmark of cancer.
- Targeting pro-survival BH proteins is a promising strategy for cancer chemotherapy.
- The BAD BH3 domain is a known inhibitor of these proteins.
Purpose of the Study:
- To investigate if helix-constrained peptides based on the BAD BH3 domain can be reduced in size to create more drug-like molecules.
- To assess the binding affinity, structural characteristics, and anti-leukemic activity of these smaller peptidomimetics.
Main Methods:
- Preparation and structural characterization of 45 linear, mono-, bi-, and tricyclic helical peptidomimetics (8-19 residues).
- In vitro assessment of Bcl-xL inhibition.
- Evaluation of leukemic T-cell killing ability.
Main Results:
- The BAD BH3 domain can be effectively downsized to 8-14 residues while retaining significant Bcl-xL binding affinity.
- Downsized mimetics exhibit higher binding efficiency indices (BEI) compared to the original BAD BH3 and stapled BH3 mimetics.
- Monocyclic and bicyclic mimetics demonstrate superior binding efficiency, approaching that of drug-like molecules.
Conclusions:
- Smaller, constrained peptidomimetics based on the BAD BH3 domain are highly efficient ligands for Bcl-xL.
- These downsized BH3 mimetics represent a promising avenue for developing novel anti-cancer therapeutics.
- The findings suggest that optimized BH3 mimetics can be significantly smaller and more drug-like than previously thought.
