Synthesis and Biological Activity of Scyllatoxin-Based BH3 Domain Mimetics Containing Two Disulfide Linkages

Area of Science:

• Biochemistry and Molecular Biology
• Protein Engineering
• Cancer Therapeutics

Background:

• B cell lymphoma 2 (BCL2) proteins regulate apoptosis; their overexpression causes resistance to cell death, contributing to cancer.
• Targeting anti-apoptotic BCL2 proteins is a key strategy for cancer therapy.
• Synthetic proteins mimicking the Bax BH3 interaction domain are being developed as novel therapeutics.

Purpose of the Study:

• To investigate the role of two disulfide linkages in the folding and biological activity of scyllatoxin-Bax (ScTx-Bax) proteins.
• To synthesize and characterize ScTx-Bax variants with specific disulfide bond arrangements.
• To assess the binding affinity of these variants to anti-apoptotic BCL2 proteins, particularly Bcl-2.

Main Methods:

• Full chemical synthesis of three ScTx-Bax sequence variants, each with two native disulfide linkages at distinct positions.
• Assessment of protein folding and native-like architecture.
• In vitro binding assays to evaluate the targeting of anti-apoptotic BCL2 proteins, including Bcl-2.

Main Results:

• Two disulfide linkages were sufficient to achieve native-like folding in ScTx-Bax proteins.
• Specific ScTx-Bax variants demonstrated in vitro targeting of Bcl-2, with binding affinity influenced by disulfide bond position.
• Structural modeling indicated that ScTx-Bax mimetics bind to Bcl-2 in configurations similar to wild-type Bax BH3 domains.

Conclusions:

• ScTx-Bax proteins with two disulfide linkages represent a viable approach for creating BH3 domain mimetics that maintain native-like conformations.
• The position of disulfide bonds critically impacts the binding affinity to Bcl-2.
• These ScTx-Bax proteins show potential as lead compounds for targeting protein-protein interactions in cancer therapy.