Intrastrand Peptide Staples That Promote β-Sheet Folding, Self-Assembly, and Amyloid Seeding

Area of Science:

• Biochemistry
• Chemical Biology
• Structural Biology

Background:

• Side chain stapling of cysteine (Cys) residues is used to constrain peptides, improving bioactivity and bioavailability.
• While effective for helical and loop structures, stabilizing beta-sheet folds using intrastrand Cys stapling is less explored.

Purpose of the Study:

• To investigate the efficacy of i→i+2 intrastrand Cys stapling in stabilizing beta-sheet structures.
• To explore the application of this method in designing constrained peptides derived from tau protein and modulating their self-assembly.

Main Methods:

• Utilized E-butenyl, butynyl, and m-xylyl linkers for i→i+2 Cys stapling in beta-hairpin model peptides.
• Determined high-resolution NMR structures to analyze the impact of staples on backbone torsions and cross-strand interactions.
• Designed and synthesized constrained beta-arch peptides from tau protein segments incorporating i→i+2 macrocyclization.

Main Results:

• i→i+2 stapling significantly enhanced the folded population of beta-hairpin peptides.
• NMR structures confirmed that staples supported canonical beta-sheet backbone torsions and stabilized cross-strand interactions.
• Intrastrand stapling of a tau peptide segment promoted self-assembly into beta-sheet-like filaments that seeded endogenous tau aggregation.

Conclusions:

• Di-Cys i→i+2 stapling is a versatile and accessible method for stabilizing beta-sheet structure.
• This approach can modulate the self-assembly of seed-competent amyloidogenic peptides, offering insights into protein aggregation.
• The developed stapling technique provides a novel tool for peptide design and studying protein misfolding diseases.